Method and apparatus for signaling of chroma quantization parameters

ABSTRACT

According to an aspect of the disclosure, a method of video decoding performed in a video decoder is provided. In the method, syntax information of a coding unit (CU) is decoded from a coded video bitstream. The syntax information is signaled in a picture header (PH) and includes chroma quantization parameter (QP) offsets in a PH level. The chroma QP offsets include at least one of a Cb offset, a Cr offset, and a CbCr offset. Further, quantization parameters for the CU are determined based on the chroma QP offsets in the PH level and a quantization parameter range offset of the CU.

INCORPORATION BY REFERENCE

This present application claims the benefit of priority to U.S.Provisional Application No. 62/981,356, “SIGNALING OF CHROMAQUANTIZATION PARAMETERS” filed on Feb. 25, 2020, which is incorporatedby reference herein in its entirety.

TECHNICAL FIELD

The present disclosure describes embodiments generally related to videocoding.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent the work is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

ITU-T VCEG (Q6/16) and ISO/IEC MPEG (JTC 1/SC 29/WG 11) published theH.265/HEVC (High Efficiency Video Coding) standard in 2013 (version 1)2014 (version 2) 2015 (version 3) and 2016 (version 4). In 2015, the twostandard organizations jointly formed the JVET (Joint Video ExplorationTeam) to explore the potential of developing the next video codingstandard beyond HEVC. In October 2017, the two standard organizationsissued the Joint Call for Proposals on Video Compression with Capabilitybeyond HEVC (CfP). By Feb. 15, 2018, total 22 CfP responses on standarddynamic range (SDR), 12 CfP responses on high dynamic range (HDR), and12 CfP responses on 360 video categories were submitted, respectively.In April 2018, all received CfP responses were evaluated in the 122MPEG/10th JVET meeting. As a result of this meeting, JVET formallylaunched the standardization process of next-generation video codingbeyond HEVC. The new standard was named Versatile Video Coding (VVC),and JVET was renamed as Joint Video Expert Team. VTM 7 is a version ofVTM (VVC Test Model). In the following, the term quantization matrix isthe same as scaling matrix.

Video coding and decoding can be performed using inter-pictureprediction with motion compensation. Uncompressed digital video caninclude a series of pictures, each picture having a spatial dimensionof, for example, 1920×1080 luminance samples and associated chrominancesamples. The series of pictures can have a fixed or variable picturerate (informally also known as frame rate), of, for example 60 picturesper second or 60 Hz. Uncompressed video has significant bitraterequirements. For example, 1080p60 4:2:0 video at 8 bit per sample(1920×1080 luminance sample resolution at 60 Hz frame rate) requiresclose to 1.5 Gbit/s bandwidth. An hour of such video requires more than600 gigabytes (GB) of storage space.

One purpose of video coding and decoding can be the reduction ofredundancy in the input video signal, through compression. Compressioncan help reduce the aforementioned bandwidth or storage spacerequirements, in some cases by two orders of magnitude or more. Bothlossless and lossy compression, as well as a combination thereof can beemployed. Lossless compression refers to techniques where an exact copyof the original signal can be reconstructed from the compressed originalsignal. When using lossy compression, the reconstructed signal may notbe identical to the original signal, but the distortion between originaland reconstructed signals is small enough to make the reconstructedsignal useful for the intended application. In the case of video, lossycompression is widely employed. The amount of distortion tolerateddepends on the application; for example, users of certain consumerstreaming applications may tolerate higher distortion than users oftelevision distribution applications. The compression ratio achievablecan reflect that: higher allowable/tolerable distortion can yield highercompression ratios.

A video encoder and decoder can utilize techniques from several broadcategories, including, for example, motion compensation, transform,quantization, and entropy coding.

Video codec technologies can include techniques known as intra coding.In intra coding, sample values are represented without reference tosamples or other data from previously reconstructed reference pictures.In some video codecs, the picture is spatially subdivided into blocks ofsamples. When all blocks of samples are coded in intra mode, thatpicture can be an intra picture. Intra pictures and their derivationssuch as independent decoder refresh pictures, can be used to reset thedecoder state and can, therefore, be used as the first picture in acoded video bitstream and a video session, or as a still image. Thesamples of an intra block can be exposed to a transform, and thetransform coefficients can be quantized before entropy coding. Intraprediction can be a technique that minimizes sample values in thepre-transform domain. In some cases, the smaller the DC value after atransform is, and the smaller the AC coefficients are, the fewer thebits that are required at a given quantization step size to representthe block after entropy coding.

Traditional intra coding such as known from, for example MPEG-2generation coding technologies, does not use intra prediction. However,some newer video compression technologies include techniques thatattempt, from, for example, surrounding sample data and/or metadataobtained during the encoding/decoding of spatially neighboring, andpreceding in decoding order, blocks of data. Such techniques arehenceforth called “intra prediction” techniques. Note that in at leastsome cases, intra prediction is only using reference data from thecurrent picture under reconstruction and not from reference pictures.

There can be many different forms of intra prediction. When more thanone of such techniques can be used in a given video coding technology,the technique in use can be coded in an intra prediction mode. Incertain cases, modes can have submodes and/or parameters, and those canbe coded individually or included in the mode codeword. Which codewordto use for a given mode/submode/parameter combination can have an impactin the coding efficiency gain through intra prediction, and so can theentropy coding technology used to translate the codewords into abitstream.

A certain mode of intra prediction was introduced with H.264, refined inH.265, and further refined in newer coding technologies such as jointexploration model (JEM), versatile video coding (VVC), and benchmark set(BMS). A predictor block can be formed using neighboring sample valuesbelonging to already available samples. Sample values of neighboringsamples are copied into the predictor block according to a direction. Areference to the direction in use can be coded in the bitstream or mayitself be predicted.

SUMMARY

The present disclosure includes embodiments related to next-generationvideo coding technologies beyond HEVC (High Efficiency Video Coding),e.g., Versatile Video Coding (VVC). In the present disclosure, methodsfor signaling a quantization parameter are provided.

According to an aspect of the disclosure, methods and apparatus forvideo decoding performed in a video decoder are provided. In the method,syntax information of a coding unit (CU) can be decoded from a codedvideo bitstream. The syntax information can be signaled in a pictureheader (PH) and include chroma quantization parameter (QP) offsets in aPH level, where the chroma QP offsets can include at least one of a Cboffset, a Cr offset, and a CbCr offset. Further, quantization parametersfor the CU can be determined based on the chroma QP offsets in the PHlevel and a quantization parameter range offset of the CU.

In some embodiments, the syntax information can be signaled in thepicture header (PH) in response to a chroma array type not being equalto zero.

In order to determine the quantization parameters for the CU, a Cbcomponent of an initial quantization parameter of the CU can beobtained. A Cr component of the initial quantization parameter of the CUcan be obtained. A Cb component of a quantization parameter offset ofthe CU in a picture parameter set (PPS) level can be obtained. A Crcomponent of the quantization parameter offset of the CU in the PPSlevel can be obtained. A Cb component of a quantization parameter offsetof the CU in a slice header (SH) level can be obtained. A Cr componentof the quantization parameter offset of the CU in the SH level can beobtained. A Cb component of a coding unit quantization parameter offsetof the CU can be obtained. A Cr component of the coding unitquantization parameter offset of the CU can be obtained.

Further, a Cb quantization parameter of the quantization parameters canbe determined based on the QP offsets in the PH level and thequantization parameter range offset of the CU. The Cb quantizationparameter can be equal to a sum of a joint Cb offset and thequantization parameter range offset. The joint Cb offset can bedetermined based on a sum of the Cb offset of the chroma QP offsets inthe PH level, the Cb component of the initial quantization parameter ofthe CU, the Cb component of the quantization parameter offset of the CUin the PPS level, the Cb component of the quantization parameter offsetof the CU in the SH level, and the Cb component of the coding unitquantization parameter offset of the CU. The joint Cb offset can belarger than or equal to a negative quantization parameter range offsetand be less than or equal to 63.

In addition, a Cr quantization parameter of the quantization parameterscan be determined based on the QP offsets in the PH level and thequantization parameter range offset of the CU. The Cr quantizationparameter can be equal to a sum of a joint Cr offset and thequantization parameter range offset. The joint Cr offset can bedetermined based on a sum of the Cr offset of the chroma QP offsets inthe PH level, the Cr component of the initial quantization parameter ofthe CU, the Cr component of the quantization parameter offset of the CUin the PPS level, the Cr component of the quantization parameter offsetof the CU in the SH level, and the Cr component of the coding unitquantization parameter offset of the CU, where the joint Cr offset canbe larger than or equal to a negative quantization parameter rangeoffset and be less than or equal to 63.

In some embodiments, a CbCr quantization parameter of the CU can bedetermined. A CbCr quantization parameter offset of the CU in a pictureparameter set (PPS) level can be obtained. A CbCr quantization parameteroffset of the CU in a slice header (SH) level can be obtained. A CbCrcoding unit quantization parameter offset of the CU can be obtained.

In the method, a CbCr quantization parameter of the quantizationparameters can be determined based on the QP offsets in the PH level andthe quantization parameter range offset of the CU. The CbCr quantizationparameter can be equal to a sum of a joint CbCr offset and thequantization parameter range offset. The joint CbCr offset can bedetermined based on a sum of the CbCr offset of the chroma QP offsets inthe PH level, the CbCr quantization parameter of the CU, the CbCrquantization parameter offset of the CU in the PPS level, the CbCrquantization parameter offset of the CU in the SH level, and the CbCrcoding unit quantization parameter offset of the CU. The joint CbCroffset can be larger than or equal to a negative quantization parameterrange offset and be less or equal to 63.

In some embodiments, a sum of the Cb component of the quantizationparameter offset of the CU in the PPS level and the Cb offset of thechroma QP offsets in the PH level can be in a range of −12 and +12 Inaddition, a sum of the Cr component of the quantization parameter offsetof the CU in the PPS level and the Cr offset of the chroma QP offsets inthe PH level can be in a range of −12 and +12. A sum of a CbCrquantization parameter offset of the CU in the PPS level and the CbCroffset of the chroma QP offsets in the PH level can be in a range of −12and +12.

According to another aspect of the disclosure, a method of videodecoding performed in a video decoder is provided. In the method,signaling information from a coded video bitstream can be acquired.First syntax information of a coding unit (CU) from the coded videobitstream can be decoded in response to the signaling information beinga first value. The first syntax information can be signaled in a pictureheader (PH) and include chroma quantization parameter (QP) offsets in aPH level. The chroma QP offsets in the PH level can include at least oneof a Cb offset, a Cr offset, and a CbCr offset. Quantization parametersfor the CU can be subsequently determined based on the QP offsets in thePH level and a quantization parameter range offset of the CU.

In some embodiments, second syntax information of the CU can be decodedfrom the coded video bitstream in response to the signaling informationbeing a second value. The second syntax information can be signaled in aslice header (SH) and include chroma quantization parameter (QP) offsetsin a SH level. The chroma QP offsets in the SH level can include atleast one of a Cb offset, a Cr offset, and a CbCr offset. Thequantization parameters for the CU can be further determined based onthe QP offsets in the SH level and the quantization parameter rangeoffset of the CU.

In some embodiments, the first syntax information can be signaled in thepicture header (PH) in response to a chroma array type not beingmonochrome or not being a chroma format 4:4;4 with a separate colorplane flag equal to 1.

In some embodiments, the second syntax information can be signaled inthe SH in response to the chroma array type not being monochrome or notbeing the chroma format 4:4;4 with the separate color plane flag equalto 1.

In order to determine the quantization parameters for the CU, a Cbcomponent of an initial quantization parameter of the CU can beobtained. A Cr component of the initial quantization parameter of the CUcan be obtained. A Cb component of a quantization parameter offset ofthe CU in a picture parameter set (PPS) level can be obtained. A Crcomponent of the quantization parameter offset of the CU in the PPSlevel can be obtained. A Cb component of a coding unit quantizationparameter offset of the CU can be obtained. A Cr component of the codingunit quantization parameter offset of the CU can be obtained.

Further, a Cb quantization parameter can be determined based on the QPoffsets in the PH level and the quantization parameter range offset ofthe CU. The Cb quantization parameter can be equal to a sum of a jointCb offset and the quantization parameter range offset. The joint Cboffset can be determined based on a sum of the Cb offset of the chromaQP offsets in the PH level, the Cb component of the initial quantizationparameter of the CU, the Cb component of the quantization parameteroffset of the CU in the PPS level, and the Cb component of the codingunit quantization parameter offset of the CU in response to thesignaling information being the first value. The joint Cb offset can belarger than or equal to a negative quantization parameter range offsetand be less than or equal to 63.

In addition, a Cr quantization parameter can be determined based on theQP offsets in the PH level and the quantization parameter range offsetof the CU. The Cr quantization parameter can be equal to a sum of ajoint Cr offset and the quantization parameter range offset. The jointCr offset can be determined based on a sum of the Cr offset of thechroma QP offsets in the PH level, the Cr component of the initialquantization parameter of the CU, the Cr component of the quantizationparameter offset of the CU in the PPS level, and the Cr component of thecoding unit quantization parameter offset of the CU in response to thesignaling information being the first value. The joint Cr offset can belarger than or equal to a negative quantization parameter range offsetand be less than or equal to 63.

In the method, a CbCr quantization parameter of the CU can be obtained.A CbCr quantization parameter offset of the CU in a picture parameterset (PPS) level can be obtained. A CbCr coding unit quantizationparameter offset of the CU can be obtained.

Moreover, a CbCr quantization parameter can be determined based on theQP offsets in the PH level and the quantization parameter range offsetof the CU. The CbCr quantization parameter can be equal to a sum of ajoint CbCr offset and the quantization parameter range offset. The jointCbCr offset can be determined based on a sum of the CbCr offset of thechroma QP offsets in the PH level, the CbCr quantization parameter ofthe CU, the CbCr quantization parameter offset of the CU in the PPSlevel, and the CbCr coding unit quantization parameter offset of the CUin response to the signaling information being the first value. Thejoint CbCr offset can be larger than or equal to a negative quantizationparameter range offset and being less than or equal to 63.

In some embodiments, a Cb quantization parameter can be determined basedon the chroma QP offsets in the SH level and the quantization parameterrange offset of the CU. The Cb quantization parameter can be equal to asum of a joint Cb offset and the quantization parameter range offset.The joint Cb offset can be determined based on a sum of the Cb offset ofthe chroma QP offsets of the CU in the SH level, the Cb component of theinitial quantization parameter of the CU, the Cb component of thequantization parameter offset of the CU in the PPS level, and the Cbcomponent of the coding unit quantization parameter offset of the CU inresponse to the signaling information being the second value. The jointCb offset can be larger than or equal to a negative quantizationparameter range offset and be less than or equal to 63.

In some embodiments, a Cr quantization parameter can be determined basedon the chroma QP offsets in the SH level and the quantization parameterrange offset of the CU. The Cr quantization parameter can be equal to asum of a joint Cr offset and the quantization parameter range offset.The joint Cr offset can be determined based on a sum of the Cr offset ofthe chroma QP offsets of the CU in the SH level, the Cr component of theinitial quantization parameter of the CU, the Cr component of thequantization parameter offset of the CU in the PPS level, and the Crcomponent of the coding unit quantization parameter offset of the CU inresponse to being the signaling information being the second value. Thejoint Cr offset can be larger than or equal to a negative quantizationparameter range offset and be less than or equal to 63.

In addition, a CbCr quantization parameter based on the chroma QPoffsets in the SH level and the quantization parameter range offset ofthe CU, wherein: the CbCr quantization parameter is equal to a sum of ajoint CbCr offset and the quantization parameter range offset, and thejoint CbCr offset can be determined based on a sum of the CbCr offset ofthe chroma QP offsets of the CU in the SH level, the CbCr quantizationparameter of the CU, the CbCr quantization parameter offset of the CU inthe PPS level, and the CbCr coding unit quantization parameter offset ofthe CU in response to the signaling information being the second value.The joint CbCr offset can be larger than or equal to a negativequantization parameter range offset and be less than or equal to 63.

In some examples, the apparatus for video decoding includes receivingcircuitry and processing circuitry that is configured to perform one ormore of the methods described above.

Aspects of the disclosure also provide non-transitory computer-readablemediums storing instructions which when executed by a computer for videodecoding cause the computer to perform one or more of the methodsdescribed above.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, the nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a schematic illustration of a simplified block diagram of acommunication system (100) in accordance with an embodiment.

FIG. 2 is a schematic illustration of a simplified block diagram of acommunication system (200) in accordance with an embodiment.

FIG. 3 is a schematic illustration of a simplified block diagram of adecoder in accordance with an embodiment.

FIG. 4 is a schematic illustration of a simplified block diagram of anencoder in accordance with an embodiment.

FIG. 5 shows a block diagram of an encoder in accordance with anotherembodiment.

FIG. 6 shows a block diagram of a decoder in accordance with anotherembodiment.

FIG. 7 shows a first flow chart outlining a process example according tosome embodiments of the disclosure.

FIG. 8 shows a second flow chart outlining a process example accordingto some embodiments of the disclosure.

FIG. 9 is a schematic illustration of a computer system in accordancewith an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 illustrates a simplified block diagram of a communication system(100) according to an embodiment of the present disclosure. Thecommunication system (100) includes a plurality of terminal devices thatcan communicate with each other, via, for example, a network (150). Forexample, the communication system (100) includes a first pair ofterminal devices (110) and (120) interconnected via the network (150).In the FIG. 1 example, the first pair of terminal devices (110) and(120) performs unidirectional transmission of data. For example, theterminal device (110) may code video data (e.g., a stream of videopictures that are captured by the terminal device (110)) fortransmission to the other terminal device (120) via the network (150).The encoded video data can be transmitted in the form of one or morecoded video bitstreams. The terminal device (120) may receive the codedvideo data from the network (150), decode the coded video data torecover the video pictures and display video pictures according to therecovered video data. Unidirectional data transmission may be common inmedia serving applications and the like.

In another example, the communication system (100) includes a secondpair of terminal devices (130) and (140) that performs bidirectionaltransmission of coded video data that may occur, for example, duringvideoconferencing. For bidirectional transmission of data, in anexample, each terminal device of the terminal devices (130) and (140)may code video data (e.g., a stream of video pictures that are capturedby the terminal device) for transmission to the other terminal device ofthe terminal devices (130) and (140) via the network (150). Eachterminal device of the terminal devices (130) and (140) also may receivethe coded video data transmitted by the other terminal device of theterminal devices (130) and (140), and may decode the coded video data torecover the video pictures and may display video pictures at anaccessible display device according to the recovered video data.

In the FIG. 1 example, the terminal devices (110), (120), (130) and(140) may be illustrated as servers, personal computers and smart phonesbut the principles of the present disclosure may be not so limited.Embodiments of the present disclosure find application with laptopcomputers, tablet computers, media players and/or dedicated videoconferencing equipment. The network (150) represents any number ofnetworks that convey coded video data among the terminal devices (110),(120), (130) and (140), including for example wireline (wired) and/orwireless communication networks. The communication network (150) mayexchange data in circuit-switched and/or packet-switched channels.Representative networks include telecommunications networks, local areanetworks, wide area networks and/or the Internet. For the purposes ofthe present discussion, the architecture and topology of the network(150) may be immaterial to the operation of the present disclosureunless explained herein below.

FIG. 2 illustrates, as an example for an application for the disclosedsubject matter, the placement of a video encoder and a video decoder ina streaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem (213), that caninclude a video source (201), for example a digital camera, creating forexample a stream of video pictures (202) that are uncompressed. In anexample, the stream of video pictures (202) includes samples that aretaken by the digital camera. The stream of video pictures (202),depicted as a bold line to emphasize a high data volume when compared toencoded video data (204) (or coded video bitstreams), can be processedby an electronic device (220) that includes a video encoder (203)coupled to the video source (201). The video encoder (203) can includehardware, software, or a combination thereof to enable or implementaspects of the disclosed subject matter as described in more detailbelow. The encoded video data (204) (or encoded video bitstream (204)),depicted as a thin line to emphasize the lower data volume when comparedto the stream of video pictures (202), can be stored on a streamingserver (205) for future use. One or more streaming client subsystems,such as client subsystems (206) and (208) in FIG. 2 can access thestreaming server (205) to retrieve copies (207) and (209) of the encodedvideo data (204). A client subsystem (206) can include a video decoder(210), for example, in an electronic device (230). The video decoder(210) decodes the incoming copy (207) of the encoded video data andcreates an outgoing stream of video pictures (211) that can be renderedon a display (212) (e.g., display screen) or other rendering device (notdepicted). In some streaming systems, the encoded video data (204),(207), and (209) (e.g., video bitstreams) can be encoded according tocertain video coding/compression standards. Examples of those standardsinclude ITU-T Recommendation H.265. In an example, a video codingstandard under development is informally known as Versatile Video Coding(VVC). The disclosed subject matter may be used in the context of VVC.

It is noted that the electronic devices (220) and (230) can includeother components (not shown). For example, the electronic device (220)can include a video decoder (not shown) and the electronic device (230)can include a video encoder (not shown) as well.

FIG. 3 shows a block diagram of a video decoder (310) according to anembodiment of the present disclosure. The video decoder (310) can beincluded in an electronic device (330). The electronic device (330) caninclude a receiver (331) (e.g., receiving circuitry). The video decoder(310) can be used in the place of the video decoder (210) in the FIG. 2example.

The receiver (331) may receive one or more coded video sequences to bedecoded by the video decoder (310); in the same or another embodiment,one coded video sequence at a time, where the decoding of each codedvideo sequence is independent from other coded video sequences. Thecoded video sequence may be received from a channel (301), which may bea hardware/software link to a storage device which stores the encodedvideo data. The receiver (331) may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver (331) may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory (315) may be coupled inbetween the receiver (331) and an entropy decoder/parser (320) (“parser(320)” henceforth). In certain applications, the buffer memory (315) ispart of the video decoder (310). In others, it can be outside of thevideo decoder (310) (not depicted). In still others, there can be abuffer memory (not depicted) outside of the video decoder (310), forexample to combat network jitter, and in addition another buffer memory(315) inside the video decoder (310), for example to handle playouttiming. When the receiver (331) is receiving data from a store/forwarddevice of sufficient bandwidth and controllability, or from anisosynchronous network, the buffer memory (315) may not be needed, orcan be small. For use on best effort packet networks such as theInternet, the buffer memory (315) may be required, can be comparativelylarge and can be advantageously of adaptive size, and may at leastpartially be implemented in an operating system or similar elements (notdepicted) outside of the video decoder (310).

The video decoder (310) may include the parser (320) to reconstructsymbols (321) from the coded video sequence. Categories of those symbolsinclude information used to manage operation of the video decoder (310),and potentially information to control a rendering device such as arender device (312) (e.g., a display screen) that is not an integralpart of the electronic device (330) but can be coupled to the electronicdevice (330), as was shown in FIG. 3. The control information for therendering device(s) may be in the form of Supplemental EnhancementInformation (SEI messages) or Video Usability Information (VUI)parameter set fragments (not depicted). The parser (320) mayparse/entropy-decode the coded video sequence that is received. Thecoding of the coded video sequence can be in accordance with a videocoding technology or standard, and can follow various principles,including variable length coding, Huffman coding, arithmetic coding withor without context sensitivity, and so forth. The parser (320) mayextract from the coded video sequence, a set of subgroup parameters forat least one of the subgroups of pixels in the video decoder, based uponat least one parameter corresponding to the group. Subgroups can includeGroups of Pictures (GOPs), pictures, tiles, slices, macroblocks, CodingUnits (CUs), blocks, Transform Units (TUs), Prediction Units (PUs) andso forth. The parser (320) may also extract from the coded videosequence information such as transform coefficients, quantizer parametervalues, motion vectors, and so forth.

The parser (320) may perform an entropy decoding/parsing operation onthe video sequence received from the buffer memory (315), so as tocreate symbols (321).

Reconstruction of the symbols (321) can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser (320). The flow of such subgroup control information between theparser (320) and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, the video decoder (310)can be conceptually subdivided into a number of functional units asdescribed below. In a practical implementation operating undercommercial constraints, many of these units interact closely with eachother and can, at least partly, be integrated into each other. However,for the purpose of describing the disclosed subject matter, theconceptual subdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit (351). Thescaler/inverse transform unit (351) receives a quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc. as symbol(s) (321) from the parser (320). The scaler/inversetransform unit (351) can output blocks comprising sample values, thatcan be input into aggregator (355).

In some cases, the output samples of the scaler/inverse transform (351)can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit (352). In some cases, the intra pictureprediction unit (352) generates a block of the same size and shape ofthe block under reconstruction, using surrounding already reconstructedinformation fetched from the current picture buffer (358). The currentpicture buffer (358) buffers, for example, partly reconstructed currentpicture and/or fully reconstructed current picture. The aggregator(355), in some cases, adds, on a per sample basis, the predictioninformation the intra prediction unit (352) has generated to the outputsample information as provided by the scaler/inverse transform unit(351).

In other cases, the output samples of the scaler/inverse transform unit(351) can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a motion compensation prediction unit (353) canaccess reference picture memory (357) to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols (321) pertaining to the block, these samples can beadded by the aggregator (355) to the output of the scaler/inversetransform unit (351) (in this case called the residual samples orresidual signal) so as to generate output sample information. Theaddresses within the reference picture memory (357) from where themotion compensation prediction unit (353) fetches prediction samples canbe controlled by motion vectors, available to the motion compensationprediction unit (353) in the form of symbols (321) that can have, forexample X, Y, and reference picture components. Motion compensation alsocan include interpolation of sample values as fetched from the referencepicture memory (357) when sub-sample exact motion vectors are in use,motion vector prediction mechanisms, and so forth.

The output samples of the aggregator (355) can be subject to variousloop filtering techniques in the loop filter unit (356). Videocompression technologies can include in-loop filter technologies thatare controlled by parameters included in the coded video sequence (alsoreferred to as coded video bitstream) and made available to the loopfilter unit (356) as symbols (321) from the parser (320), but can alsobe responsive to meta-information obtained during the decoding ofprevious (in decoding order) parts of the coded picture or coded videosequence, as well as responsive to previously reconstructed andloop-filtered sample values.

The output of the loop filter unit (356) can be a sample stream that canbe output to the render device (312) as well as stored in the referencepicture memory (357) for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. For example, once a codedpicture corresponding to a current picture is fully reconstructed andthe coded picture has been identified as a reference picture (by, forexample, the parser (320)), the current picture buffer (358) can becomea part of the reference picture memory (357), and a fresh currentpicture buffer can be reallocated before commencing the reconstructionof the following coded picture.

The video decoder (310) may perform decoding operations according to apredetermined video compression technology in a standard, such as ITU-TRec. H.265. The coded video sequence may conform to a syntax specifiedby the video compression technology or standard being used, in the sensethat the coded video sequence adheres to both the syntax of the videocompression technology or standard and the profiles as documented in thevideo compression technology or standard. Specifically, a profile canselect certain tools as the only tools available for use under thatprofile from all the tools available in the video compression technologyor standard. Also necessary for compliance can be that the complexity ofthe coded video sequence is within bounds as defined by the level of thevideo compression technology or standard. In some cases, levels restrictthe maximum picture size, maximum frame rate, maximum reconstructionsample rate (measured in, for example megasamples per second), maximumreference picture size, and so on. Limits set by levels can, in somecases, be further restricted through Hypothetical Reference Decoder(HRD) specifications and metadata for HRD buffer management signaled inthe coded video sequence.

In an embodiment, the receiver (331) may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder (310) to properly decode the data and/or to moreaccurately reconstruct the original video data. Additional data can bein the form of, for example, temporal, spatial, or signal noise ratio(SNR) enhancement layers, redundant slices, redundant pictures, forwarderror correction codes, and so on.

FIG. 4 shows a block diagram of a video encoder (403) according to anembodiment of the present disclosure. The video encoder (403) isincluded in an electronic device (420). The electronic device (420)includes a transmitter (440) (e.g., transmitting circuitry). The videoencoder (403) can be used in the place of the video encoder (203) in theFIG. 2 example.

The video encoder (403) may receive video samples from a video source(401) (that is not part of the electronic device (420) in the FIG. 4example) that may capture video image(s) to be coded by the videoencoder (403). In another example, the video source (401) is a part ofthe electronic device (420).

The video source (401) may provide the source video sequence to be codedby the video encoder (403) in the form of a digital video sample streamthat can be of any suitable bit depth (for example: 8 bit, 10 bit, 12bit, . . . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . ),and any suitable sampling structure (for example Y CrCb 4:2:0, Y CrCb4:4:4). In a media serving system, the video source (401) may be astorage device storing previously prepared video. In a videoconferencingsystem, the video source (401) may be a camera that captures local imageinformation as a video sequence. Video data may be provided as aplurality of individual pictures that impart motion when viewed insequence. The pictures themselves may be organized as a spatial array ofpixels, wherein each pixel can comprise one or more samples depending onthe sampling structure, color space, etc. in use. A person skilled inthe art can readily understand the relationship between pixels andsamples. The description below focuses on samples.

According to an embodiment, the video encoder (403) may code andcompress the pictures of the source video sequence into a coded videosequence (443) in real time or under any other time constraints asrequired by the application. Enforcing appropriate coding speed is onefunction of a controller (450). In some embodiments, the controller(450) controls other functional units as described below and isfunctionally coupled to the other functional units. The coupling is notdepicted for clarity. Parameters set by the controller (450) can includerate control related parameters (picture skip, quantizer, lambda valueof rate-distortion optimization techniques, . . . ), picture size, groupof pictures (GOP) layout, maximum motion vector search range, and soforth. The controller (450) can be configured to have other suitablefunctions that pertain to the video encoder (403) optimized for acertain system design.

In some embodiments, the video encoder (403) is configured to operate ina coding loop. As an oversimplified description, in an example, thecoding loop can include a source coder (430) (e.g., responsible forcreating symbols, such as a symbol stream, based on an input picture tobe coded, and a reference picture(s)), and a (local) decoder (433)embedded in the video encoder (403). The decoder (433) reconstructs thesymbols to create the sample data in a similar manner as a (remote)decoder also would create (as any compression between symbols and codedvideo bitstream is lossless in the video compression technologiesconsidered in the disclosed subject matter). The reconstructed samplestream (sample data) is input to the reference picture memory (434). Asthe decoding of a symbol stream leads to bit-exact results independentof decoder location (local or remote), the content in the referencepicture memory (434) is also bit exact between the local encoder andremote encoder. In other words, the prediction part of an encoder “sees”as reference picture samples exactly the same sample values as a decoderwould “see” when using prediction during decoding. This fundamentalprinciple of reference picture synchronicity (and resulting drift, ifsynchronicity cannot be maintained, for example because of channelerrors) is used in some related arts as well.

The operation of the “local” decoder (433) can be the same as of a“remote” decoder, such as the video decoder (310), which has alreadybeen described in detail above in conjunction with FIG. 3. Brieflyreferring also to FIG. 3, however, as symbols are available andencoding/decoding of symbols to a coded video sequence by an entropycoder (445) and the parser (320) can be lossless, the entropy decodingparts of the video decoder (310), including the buffer memory (315), andparser (320) may not be fully implemented in the local decoder (433).

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. For this reason, thedisclosed subject matter focuses on decoder operation. The descriptionof encoder technologies can be abbreviated as they are the inverse ofthe comprehensively described decoder technologies. Only in certainareas a more detail description is required and provided below.

During operation, in some examples, the source coder (430) may performmotion compensated predictive coding, which codes an input picturepredictively with reference to one or more previously-coded picture fromthe video sequence that were designated as “reference pictures”. In thismanner, the coding engine (432) codes differences between pixel blocksof an input picture and pixel blocks of reference picture(s) that may beselected as prediction reference(s) to the input picture.

The local video decoder (433) may decode coded video data of picturesthat may be designated as reference pictures, based on symbols createdby the source coder (430). Operations of the coding engine (432) mayadvantageously be lossy processes. When the coded video data may bedecoded at a video decoder (not shown in FIG. 4), the reconstructedvideo sequence typically may be a replica of the source video sequencewith some errors. The local video decoder (433) replicates decodingprocesses that may be performed by the video decoder on referencepictures and may cause reconstructed reference pictures to be stored inthe reference picture cache (434). In this manner, the video encoder(403) may store copies of reconstructed reference pictures locally thathave common content as the reconstructed reference pictures that will beobtained by a far-end video decoder (absent transmission errors).

The predictor (435) may perform prediction searches for the codingengine (432). That is, for a new picture to be coded, the predictor(435) may search the reference picture memory (434) for sample data (ascandidate reference pixel blocks) or certain metadata such as referencepicture motion vectors, block shapes, and so on, that may serve as anappropriate prediction reference for the new pictures. The predictor(435) may operate on a sample block-by-pixel block basis to findappropriate prediction references. In some cases, as determined bysearch results obtained by the predictor (435), an input picture mayhave prediction references drawn from multiple reference pictures storedin the reference picture memory (434).

The controller (450) may manage coding operations of the source coder(430), including, for example, setting of parameters and subgroupparameters used for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder (445). The entropy coder (445)translates the symbols as generated by the various functional units intoa coded video sequence, by lossless compressing the symbols according totechnologies such as Huffman coding, variable length coding, arithmeticcoding, and so forth.

The transmitter (440) may buffer the coded video sequence(s) as createdby the entropy coder (445) to prepare for transmission via acommunication channel (460), which may be a hardware/software link to astorage device which would store the encoded video data. The transmitter(440) may merge coded video data from the video coder (403) with otherdata to be transmitted, for example, coded audio data and/or ancillarydata streams (sources not shown).

The controller (450) may manage operation of the video encoder (403).During coding, the controller (450) may assign to each coded picture acertain coded picture type, which may affect the coding techniques thatmay be applied to the respective picture. For example, pictures oftenmay be assigned as one of the following picture types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other picture in the sequence as a source ofprediction. Some video codecs allow for different types of intrapictures, including, for example Independent Decoder Refresh (“IDR”)Pictures. A person skilled in the art is aware of those variants of Ipictures and their respective applications and features.

A predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A bi-directionally predictive picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded predictively, viaspatial prediction or via temporal prediction with reference to onepreviously coded reference picture. Blocks of B pictures may be codedpredictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video encoder (403) may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video encoder (403) may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter (440) may transmit additional datawith the encoded video. The source coder (430) may include such data aspart of the coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, SEI messages, VUI parameter setfragments, and so on.

A video may be captured as a plurality of source pictures (videopictures) in a temporal sequence. Intra-picture prediction (oftenabbreviated to intra prediction) makes use of spatial correlation in agiven picture, and inter-picture prediction makes uses of the (temporalor other) correlation between the pictures. In an example, a specificpicture under encoding/decoding, which is referred to as a currentpicture, is partitioned into blocks. When a block in the current pictureis similar to a reference block in a previously coded and still bufferedreference picture in the video, the block in the current picture can becoded by a vector that is referred to as a motion vector. The motionvector points to the reference block in the reference picture, and canhave a third dimension identifying the reference picture, in casemultiple reference pictures are in use.

In some embodiments, a bi-prediction technique can be used in theinter-picture prediction. According to the bi-prediction technique, tworeference pictures, such as a first reference picture and a secondreference picture that are both prior in decoding order to the currentpicture in the video (but may be in the past and future, respectively,in display order) are used. A block in the current picture can be codedby a first motion vector that points to a first reference block in thefirst reference picture, and a second motion vector that points to asecond reference block in the second reference picture. The block can bepredicted by a combination of the first reference block and the secondreference block.

Further, a merge mode technique can be used in the inter-pictureprediction to improve coding efficiency.

According to some embodiments of the disclosure, predictions, such asinter-picture predictions and intra-picture predictions are performed inthe unit of blocks. For example, according to the HEVC standard, apicture in a sequence of video pictures is partitioned into coding treeunits (CTU) for compression, the CTUs in a picture have the same size,such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTUincludes three coding tree blocks (CTBs), which are one luma CTB and twochroma CTBs. Each CTU can be recursively quadtree split into one ormultiple coding units (CUs). For example, a CTU of 64×64 pixels can besplit into one CU of 64×64 pixels, or 4 CUs of 32×32 pixels, or 16 CUsof 16×16 pixels. In an example, each CU is analyzed to determine aprediction type for the CU, such as an inter prediction type or an intraprediction type. The CU is split into one or more prediction units (PUs)depending on the temporal and/or spatial predictability. Generally, eachPU includes a luma prediction block (PB), and two chroma PBs. In anembodiment, a prediction operation in coding (encoding/decoding) isperformed in the unit of a prediction block. Using a luma predictionblock as an example of a prediction block, the prediction block includesa matrix of values (e.g., luma values) for pixels, such as 8×8 pixels,16×16 pixels, 8×16 pixels, 16×8 pixels, and the like.

FIG. 5 shows a diagram of a video encoder (503) according to anotherembodiment of the disclosure. The video encoder (503) is configured toreceive a processing block (e.g., a prediction block) of sample valueswithin a current video picture in a sequence of video pictures, andencode the processing block into a coded picture that is part of a codedvideo sequence. In an example, the video encoder (503) is used in theplace of the video encoder (203) in the FIG. 2 example.

In an HEVC example, the video encoder (503) receives a matrix of samplevalues for a processing block, such as a prediction block of 8×8samples, and the like. The video encoder (503) determines whether theprocessing block is best coded using intra mode, inter mode, orbi-prediction mode using, for example, rate-distortion optimization.When the processing block is to be coded in intra mode, the videoencoder (503) may use an intra prediction technique to encode theprocessing block into the coded picture; and when the processing blockis to be coded in inter mode or bi-prediction mode, the video encoder(503) may use an inter prediction or bi-prediction technique,respectively, to encode the processing block into the coded picture. Incertain video coding technologies, merge mode can be an inter pictureprediction submode where the motion vector is derived from one or moremotion vector predictors without the benefit of a coded motion vectorcomponent outside the predictors. In certain other video codingtechnologies, a motion vector component applicable to the subject blockmay be present. In an example, the video encoder (503) includes othercomponents, such as a mode decision module (not shown) to determine themode of the processing blocks.

In the FIG. 5 example, the video encoder (503) includes the interencoder (530), an intra encoder (522), a residue calculator (523), aswitch (526), a residue encoder (524), a general controller (521), andan entropy encoder (525) coupled together as shown in FIG. 5.

The inter encoder (530) is configured to receive the samples of thecurrent block (e.g., a processing block), compare the block to one ormore reference blocks in reference pictures (e.g., blocks in previouspictures and later pictures), generate inter prediction information(e.g., description of redundant information according to inter encodingtechnique, motion vectors, merge mode information), and calculate interprediction results (e.g., predicted block) based on the inter predictioninformation using any suitable technique. In some examples, thereference pictures are decoded reference pictures that are decoded basedon the encoded video information.

The intra encoder (522) is configured to receive the samples of thecurrent block (e.g., a processing block), in some cases compare theblock to blocks already coded in the same picture, generate quantizedcoefficients after transform, and in some cases also intra predictioninformation (e.g., an intra prediction direction information accordingto one or more intra encoding techniques). In an example, the intraencoder (522) also calculates intra prediction results (e.g., predictedblock) based on the intra prediction information and reference blocks inthe same picture.

The general controller (521) is configured to determine general controldata and control other components of the video encoder (503) based onthe general control data. In an example, the general controller (521)determines the mode of the block, and provides a control signal to theswitch (526) based on the mode. For example, when the mode is the intramode, the general controller (521) controls the switch (526) to selectthe intra mode result for use by the residue calculator (523), andcontrols the entropy encoder (525) to select the intra predictioninformation and include the intra prediction information in thebitstream; and when the mode is the inter mode, the general controller(521) controls the switch (526) to select the inter prediction resultfor use by the residue calculator (523), and controls the entropyencoder (525) to select the inter prediction information and include theinter prediction information in the bitstream.

The residue calculator (523) is configured to calculate a difference(residue data) between the received block and prediction resultsselected from the intra encoder (522) or the inter encoder (530). Theresidue encoder (524) is configured to operate based on the residue datato encode the residue data to generate the transform coefficients. In anexample, the residue encoder (524) is configured to convert the residuedata from a spatial domain to a frequency domain, and generate thetransform coefficients. The transform coefficients are then subject toquantization processing to obtain quantized transform coefficients. Invarious embodiments, the video encoder (503) also includes a residuedecoder (528). The residue decoder (528) is configured to performinverse-transform, and generate the decoded residue data. The decodedresidue data can be suitably used by the intra encoder (522) and theinter encoder (530). For example, the inter encoder (530) can generatedecoded blocks based on the decoded residue data and inter predictioninformation, and the intra encoder (522) can generate decoded blocksbased on the decoded residue data and the intra prediction information.The decoded blocks are suitably processed to generate decoded picturesand the decoded pictures can be buffered in a memory circuit (not shown)and used as reference pictures in some examples.

The entropy encoder (525) is configured to format the bitstream toinclude the encoded block. The entropy encoder (525) is configured toinclude various information according to a suitable standard, such asthe HEVC standard. In an example, the entropy encoder (525) isconfigured to include the general control data, the selected predictioninformation (e.g., intra prediction information or inter predictioninformation), the residue information, and other suitable information inthe bitstream. Note that, according to the disclosed subject matter,when coding a block in the merge submode of either inter mode orbi-prediction mode, there is no residue information.

FIG. 6 shows a diagram of a video decoder (610) according to anotherembodiment of the disclosure. The video decoder (610) is configured toreceive coded pictures that are part of a coded video sequence, anddecode the coded pictures to generate reconstructed pictures. In anexample, the video decoder (610) is used in the place of the videodecoder (210) in the FIG. 2 example.

In the FIG. 6 example, the video decoder (610) includes an entropydecoder (671), an inter decoder (680), a residue decoder (673), areconstruction module (674), and an intra decoder (672) coupled togetheras shown in FIG. 6.

The entropy decoder (671) can be configured to reconstruct, from thecoded picture, certain symbols that represent the syntax elements ofwhich the coded picture is made up. Such symbols can include, forexample, the mode in which a block is coded (such as, for example, intramode, inter mode, bi-predicted mode, the latter two in merge submode oranother submode), prediction information (such as, for example, intraprediction information or inter prediction information) that canidentify certain sample or metadata that is used for prediction by theintra decoder (672) or the inter decoder (680), respectively, residualinformation in the form of, for example, quantized transformcoefficients, and the like. In an example, when the prediction mode isinter or bi-predicted mode, the inter prediction information is providedto the inter decoder (680); and when the prediction type is the intraprediction type, the intra prediction information is provided to theintra decoder (672). The residual information can be subject to inversequantization and is provided to the residue decoder (673).

The inter decoder (680) is configured to receive the inter predictioninformation, and generate inter prediction results based on the interprediction information.

The intra decoder (672) is configured to receive the intra predictioninformation, and generate prediction results based on the intraprediction information.

The residue decoder (673) is configured to perform inverse quantizationto extract de-quantized transform coefficients, and process thede-quantized transform coefficients to convert the residual from thefrequency domain to the spatial domain. The residue decoder (673) mayalso require certain control information (to include the QuantizerParameter (QP)), and that information may be provided by the entropydecoder (671) (data path not depicted as this may be low volume controlinformation only).

The reconstruction module (674) is configured to combine, in the spatialdomain, the residual as output by the residue decoder (673) and theprediction results (as output by the inter or intra prediction modulesas the case may be) to form a reconstructed block, that may be part ofthe reconstructed picture, which in turn may be part of thereconstructed video. It is noted that other suitable operations, such asa deblocking operation and the like, can be performed to improve thevisual quality.

It is noted that the video encoders (203), (403), and (503), and thevideo decoders (210), (310), and (610) can be implemented using anysuitable technique. In an embodiment, the video encoders (203), (403),and (503), and the video decoders (210), (310), and (610) can beimplemented using one or more integrated circuits. In anotherembodiment, the video encoders (203), (403), and (403), and the videodecoders (210), (310), and (610) can be implemented using one or moreprocessors that execute software instructions.

In a video coding process, quantization parameters (QPs) may need to bechanged within a picture for rate control and perceptual quantizationpurposes, for example.

In VVC Draft 8, a QP can be controlled in a high-level syntax (orhigh-level control) such as a picture parameter set (PPS), a pictureheader (PH), or a slice header (SH), and can also be controlled in alow-level syntax such as a coding block or a transform block.

For a high level control of a luma QP, an initial QP value can besignaled in the PPS, and a flag can also be signaled in the PPS toindicate that an additional QP offset is either signaled in the PH orthe SH. Therefore, a luma QP granularity can be achieved by adding theQP offset to the initial QP value. Table 1 illustrates exemplary luma QPrelated syntax elements signalled in PPS.

TABLE 1 Luma QP related syntax elements in PPS Descriptorpic_parameter_set_rbsp( ) { ... init_qp_minus26 se(v) ...qp_delta_info_in_ph_flag u(1) ... }

As shown in Table 1, init_qp_minus26 plus 26 can specify an initialvalue of SliceQpY for each slice that refers to a corresponding PPS. Theinitial value of SliceQpY can be modified at the picture level when anon-zero value of ph_qp_delta is decoded or at the slice level when anon-zero value of slice_qp_delta is decoded. The value ofinit_qp_minus26 can be in a range of −(26+QpBdOffset) to +37, inclusive.In addition, qp_delta_info_inph_flag equal to 1 can specify that QPdelta information is present in the PH syntax structure and not presentin the slice headers, where the slice headers refer to the PPS that donot contain a PH syntax structure. qp_delta_info_inph_flag equal to 0can specify that QP delta information is not present in the PH syntaxstructure and may be present in slice headers, where the slice headersrefer to the PPS that does not contain a PH syntax structure.

Table 2 shows exemplary luma QP related syntax elements in a PH. Asshown in Table 2, ph_qp_delta can specify the initial value of QpY thatcan be used for coding blocks in a picture until the initial value ismodified by the value of CuQpDeltaVal in the coding unit layer. Whenqp_delta_info_in_ph_flag is equal to 1, the initial value of thequantization parameter QpY for all slices of the picture, which can bedenoted as SliceQpY, can be derived in Equation (1):SliceQpY=26+init_qp_minus26+ph_qp_delta   Eq. (1)where the value of SliceQpY can be in the range of −QpBdOffset to +63,inclusive.

TABLE 2 Luma QP related syntax elements in PH Descriptorpicture_header_structure( ) { ... if( qp_delta_info_in_ph_flag )ph_qp_delta se(v) ... }

Table 3 shows exemplary luma QP related syntax elements in SH. As shownin Table 3, slice_qp_delta can specify the initial value of QpY that isused for the coding blocks in the slice until the initial value ismodified by the value of CuQpDeltaVal in the coding unit layer. Whenqp_delta_info_in_ph_flag is equal to 0, the initial value of thequantization parameter QpY for the slice, which can be denoted asSliceQpY, can be derived as follows in Equation (2):SliceQpY=26+init_qp_minus26+slice_qp_delta   Eq. (2)The value of SliceQpY can be in the range of −QpBdOffset to +63,inclusive. In VVC Draft 8, chroma QP values can be derived by addingchroma QP offsets to the mapped chroma value qPCb, qPCr, and qPCbCr.Those chroma QP offsets can both be signaled in a PPS and a SH but notin a PH.

TABLE 3 Luma QP related syntax elements in SH Descriptor slice_header( ){ ... if( !qp_delta_info_in_ph_flag ) slice_qp_delta se(v) ... }

Table 4 shows exemplary chroma QP offsets related syntax elements in aPPS. As shown in Table 4, pps_chroma_tool_offsets_present_flag equal to1 can specify that chroma tool offsets related syntax elements arepresent in the PPS RBSP syntax structure.pps_chroma_tool_offsets_present_flag equal to 0 can specify that chromatool offsets related syntax elements are not present in the PPS RBSPsyntax structure. When ChromaArrayType is equal to 0, the value ofpps_chroma_tool_offsets_present_flag can be equal to 0.

TABLE 4 Chroma QP offsets related syntax elements in PPS Descriptorpic_parameter_set_rbsp( ) { ... pps_chroma_tool_offsets_present_flagu(1) if( pps_chroma_tool_offsets_present_flag ) { pps_cb_qp_offset se(v)pps_cr_qp_offset se(v) pps_joint_cbcr_qp_offset_present_flag u(1) if(pps_joint_cbcr_qp_offset_present_flag) pps_joint_cbcr_qp_offset_valuese(v) pps_slice_chroma_qp_offsets_present_flag u(1) ... } ... }

Still referring to Table 4, pps_cb_qp_offset and pps_cr_qp_offset canspecify the offsets to the luma quantization parameter Qp′Y used forderiving Qp′Cb and Qp′Cr, respectively. The values of pps_cb_qp_offsetand pps_cr_qp_offset can be in the range of −12 to +12, inclusive. WhenChromaArrayType is equal to 0, pps_cb_qp_offset and pp_cr_qp_offset maynot be used in the decoding process, and decoders accordingly can ignorethe values of the pps_cb_qp_offset and pp_cr_qp_offset. WhenChromaArrayType is not present, the values of pps_cb_qp_offset andpp_cr_qp_offset can be inferred to be equal to 0.

In Table 4, pps_joint_cbcr_qp_offset_present_flag equal to 1 can specifythat pps_joint_cbcr_qp_offset_value and joint_cbcr_qp_offset_list[i] arepresent in the PPS RBSP syntax structure.pps_joint_cbcr_qp_offset_present_flag equal to 0 can specify thatpps_joint_cbcr_qp_offset_value and joint_cbcr_qp_offset_list[i] are notpresent in the PPS RBSP syntax structure. When ChromaArrayType is equalto 0 or sps_joint_cbcr_enabled_flag is equal to 0, the value ofpps_joint_cbcr_qp_offset_present_flag can be equal to 0. WhenChromaArrayType is not present, the value ofpps_joint_cbcr_qp_offset_present_flag is inferred to be equal to 0.

Further, pps_joint_cbcr_qp_offset_value can specify the offset to theluma quantization parameter QP′Y used for deriving Q′CbCr. The value ofpps_joint_cbcr_qp_offset_value can be in the range of −12 to +12,inclusive. When ChromaArrayType is equal to 0 orsps_joint_cbcr_enabled_flag is equal to 0,pps_joint_cbcr_qp_offset_value may not be used in the decoding process,and decoders can ignore the value of pps_joint_cbcr_qp_offset_value.When pps_joint_cbcr_qp_offsetpresent_flag is equal to 0,pps_joint_cbcr_qp_offset_value may not be present and can be inferred tobe equal to 0.

pps_slice_chroma_qp_offsets_present_flag equal to 1 can indicate thatthe slice_cb_qp_offset and slice_cr_qp_offset syntax elements arepresent in the associated slice headers.pps_slice_chroma_qp_offsets_present_flag equal to 0 can indicate thatthe slice_cb_qp_offset and slice_cr_qp_offset are not present in theassociated slice headers. When presentChromaArrayType is equal to 0, thevalue of pps_slice_chroma_qp_offsets_present_flag can be inferred to beequal to 0.

Table 5 shows exemplary chroma QP offsets related syntax elements in aSH. As shown in Table 5, slice_cb_qp_offset can specify a difference tobe added to the value of pps_cb_qp_offset when the value of thequantization parameter Qp′Cb is determined. The value ofslice_cb_qp_offset can be in the range of −12 to +12, inclusive. Whenslice_cb_qp_offset is not present, it can be inferred to be equal to 0.The value of pps_cb_qp_offset+slice_cb_qp_offset can be in the range of−12 to +12, inclusive.

TABLE 5 Chroma QP offsets related syntax elements in SH Descriptorslice_header( ) { ... if( pps_slice_chroma_qp_offsets_present_flag ) {slice_cb_qp_offset se(v) slice_cr_qp_off set se(v) if(sps_joint_cbcr_enabled_flag ) slice_joint_cbcr_qp_offset se(v) } ... }

In Table 5, slice_cr_qp_offset can specify a difference to be added tothe value of pp_cr_qp_offset when the value of the Qp′Cr quantizationparameter is determined. The value of slice_cr_qp_offset can be in therange of −12 to +12, inclusive. When slice_cr_qp_offset is not present,it can be inferred to be equal to 0. The value ofpp_cr_qp_offset+slice_cr_qp_offset can be in the range of −12 to +12,inclusive.

slice_joint_cbcr_qp_offset can specify a difference to be added to thevalue of pps_joint_cbcr_qp_offset_value when the value of the Qp′CbCr isdetermined. The value of slice_joint_cbcr_qp_offset can be in the rangeof −12 to +12, inclusive. When slice_joint_cbcr_qp_offset is notpresent, it can be inferred to be equal to 0. The value ofpps_joint_cbcr_qp_offset_value+slice_joint_cbcr_qp_offset can be in therange of −12 to +12, inclusive.

In VVC Draft 8, the variable ChromaArrayType can depend on the chromaformat sampling structure, which is specified through chroma_format_idcand separate_colour_plane_flag. Table 6 shows values of ChromaArrayTypeand corresponding chroma format identifications, chroma formats, andflags (e.g., separate_colour_plane_flag).

TABLE 6 Values of ChromaArrayType chroma_format_idcseparate_colour_plane_flag Chroma format ChromaArrayType 0 0 Monochrome0 1 0 4:2:0 1 2 0 4:2:2 2 3 0 4:4:4 3 3 1 4:4:4 0As shown in Table 6, ChromaArrayType can be equal to 0 whenChromaArrayType is monochrome or is a chroma format 4:4:4 withseparate_colour_plane_flag being equal to 1.

In VVC Draft 8, chroma QP granularity can only be achieved in a PPS or aSH. In the present disclosure, chroma QP offsets can be signalled in aPH in some embodiments. Examples of corresponding syntax elements thatcan be included as illustrated in Table 7.

TABLE 7 Syntax elements to signal chroma QP offsets in PH Descriptorpicture_header_structure( ) { ... ph_cb_qp_offset se(v) ph_cr_qp_offsetse(v) ... }

As show in Table 7, ph_cb_qp_offset and ph_cr_qp_offset can specifyoffsets to the luma quantization parameter Qp′Y used for deriving Qp′Cband Qp′Cr, respectively. The values of ph_cb_qp_offset andph_cr_qp_offset can be in the range of −12 to +12, inclusive. Whenph_cb_qp_offset and ph_cr_qp_offset are not present, the values ofph_cb_qp_offset and ph_cr_qp_offset can be inferred to be equal to 0.The value of pps_cb_qp_offset+ph_cb_qp_offset can be in the range of −12to +12, inclusive. The value of pp_cr_qp_offset+ph_cr_qp_offset can bein the range of −12 to +12, inclusive.

In an embodiment, chroma QP offsets can be conditionally signaled in aPH based on chroma color format. For example, when only ChromaArrayTypeis not equal to 0, ph_cb_qp_offset and ph_cr_qp_offset can be signaled.In other words, when no chroma component is present in the bitstream,ph_cb_qp_offset and ph_cr_qp_offset are not signaled. Examples ofcorresponding syntax elements are illustrated in Table 8.

TABLE 8 Syntax elements to signal chroma QP offsets in PH according toChromaArrayType Descriptor picture_header_structure( ) { ... if(ChromaArrayType !=0) { ph_cb_qp_offset se(v) ph_cr_qp_offset se(v) ...} ... }As shown in Table 8, ph_cb_qp_offset and ph_cr_qp_offset can specify theoffsets to the luma quantization parameter Qp′Y used for deriving Qp′Cband Qp′Cr, respectively. The values of ph_cb_qp_offset andph_cr_qp_offset can be in the range of −12 to +12, inclusive. Whenph_cb_qp_offset and ph_cr_qp_offset are not present, the values ofph_cb_qp_offset and ph_cr_qp_offset can be inferred to be equal to 0.The value of pps_cb_qp_offset+ph_cb_qp_offset can be in the range of −12to +12, inclusive. The value of pp_cr_qp_offset+ph_cr_qp_offset can bein the range of −12 to +12, inclusive.

According to Tables 7 and 8, both QP offsets signaled in a PH and a SHcan be applied to derive chroma QP values in order to achieve bettergranularity of a QP. In one embodiment, chroma QP values are derived asfollows in Equations (3) and (4):QP′ _(Cb)=Clip3(−QpBdOffset, 63, qP _(Cb)+pps_cb_qp_offset+ph_cb_qp_offset+slice_cb_qp_offset+CuQpOffset_(Cb))+QpBdOffset  Eq. (3)QP′ _(Cr)=Clip3(−QpBdOffset, 63, qP _(Cr)+pps_cr_qp_offset+ph_cr_qp_offset+slice_cr_qp_offset+CuQpOffset_(Cr))+QpBdOffset  Eq. (4)In Equations (3) and (4), Bd stands for bit depth (BitDepth) of thesamples of the luma and chroma arrays, and QpBdOffset denotes the valueof the luma and chroma quantization parameter range offset. BitDepth andQpBdOffset can be defined in Equations (5) and (6) respectively:BitDepth=8+sps_bitdepth_minus   Eq. (5)QpBdOffset=6*sps_bitdepth_minus8   Eq. (6)

As shown in Equation (3), a Cb quantization parameter (e.g., QP′cb) canbe equal to a sum of a joint Cb offset and the quantization parameterrange offset (e.g., QpBdOffset). The joint Cb offset can be determinedbased on a sum of a Cb offset of the chroma QP offsets in a PH level(e.g., ph_cb_qp_offset), a Cb component of the initial quantizationparameter of the CU (e.g., qP_(Cb)), a Cb component of the quantizationparameter offset of the CU in a PPS level (e.g., pps_cb_qp_offset), a Cbcomponent of the quantization parameter offset of the CU in a SH level(e.g., slice_cb_qp_offset), and the Cb component of the coding unitquantization parameter offset of the CU (e.g., CuQpOffset_(Cb)).According to the function Clip3 (x, y, z), the joint Cb offset can belarger than or equal to a negative quantization parameter range offset(e.g., −QpBdOffset) and being less than or equal to 63.

Also, according to Equation (4), a Cr quantization parameter QP′cr canbe equal to a sum of a joint Cr offset and the quantization parameterrange offset (e.g., QpBdOffset). The joint Cr offset can be determinedbased on a sum of a Cr offset of the chroma QP offsets in a PH level(e.g., ph_cr_qp_offset), a Cr component of the initial quantizationparameter of the CU (e.g., gP_(Cr)), a Cr component of the quantizationparameter offset of the CU in a PPS level (e.g., pp_cr_qp_offset), a Crcomponent of the quantization parameter offset of the CU in a SH level(e.g., slice_cr_qp_offset), and the Cr component of the coding unitquantization parameter offset of the CU (e.g., CuQpOffset_(Cr)).According to the function Clip3 (x, y, z), the joint Cb offset can belarger than or equal to the negative quantization parameter range offset(e.g., −QpBdOffset) and being less than or equal to 63.

In an embodiment, a signal can be signalled to indicate either a QPoffset is signaled in PH or SH in order to derive a chroma QP value. Theflag can also be used to condition the QP offset value. In an example,the flag, which is denoted as chroma_qp_offset_info_in_ph_flag, can besignaled in a PPS, and the related syntax elements can be illustrated inTable 9 for example.

TABLE 9 Syntax elements to signal a flagchroma_qp_offset_info_in_ph_flag in PPS Descriptorpic_parameter_set_rbsp( ) { ... pps_chroma_tool_offsets_present flagu(l) if( pps_chroma_tool_offsets_present_flag ) { ...chroma_qp_offset_info_in_ph_flag u(l) ... } ... }

As shown in Table 9, chroma_qp_offset_info_in_ph_flag equal to a firstvalue (e.g., 1) can specify that chroma QP offset information is presentin the PH syntax structure and not present in slice headers, where theslice headers refer to the PPS that do not contain a PH syntaxstructure. chroma_qp_offset_info_in_ph_flag equal to a second value(e.g., 0) can specify that QP delta information is not present in the PHsyntax structure and may be present in slice headers, where the sliceheaders refer to the PPS that do not contain a PH syntax structure. Whenchroma_qp_offset_info_in_ph_flag is not present, it can be inferred tobe equal to 0.

Table 10 shows exemplary syntax elements to signal a QP offset in a PH.

TABLE 10 syntax elements to signal a QP offset in PH Descriptorpicture_header_structure( ) { ... if (ChromaArrayType !=0) { if (chroma_qp_offset_info_in_ph_flag) { ph_cb_qp_offset se(v)ph_cr_qp_offset se(v) } } ... }As shown in Table 10, when chroma_qp_offset_info_in_ph_flag is true orequal to the first value (e.g., 1), and ChromaArrayType is not equal tozero, ph_cb_qp_offset and ph_cr_qp_offset can be signaled.ph_cb_qp_offset and ph_cr_qp_offset can specify the offsets to the lumaquantization parameter Qp′Y used for deriving Qp′Cb and Qp′Cr,respectively. The values of ph_cb_qp_offset and ph_cr_qp_offset can bein the range of −12 to +12, inclusive. When ph_cb_qp_offset andph_cr_qp_offset are not present, the values of ph_cb_qp_offset andph_cr_qp_offset can be inferred to be equal to 0. The value ofpps_cb_qp_offset+ph_cb_qp_offset can be in the range of −12 to +12,inclusive. The value of pp_cr_qp_offset+ph_cr_qp_offset can be in therange of −12 to +12, inclusive.

Table 11 shows exemplary syntax elements that can be used to signal a QPoffset in a SH. As shown in Table 9, whenchroma_qp_offset_info_in_ph_flag is not present or is equal to thesecond value (e.g., 0), and ChromaArrayType is not equal to zero,slice_cb_qp_offset and slice_cr_qp_offset can be signaled in the SH.

TABLE 11 Syntax elements to signal a QP offset in SH Descriptorslice_header( ) { ... if (ChromaArrayType !=0) { if (!chroma_qp_offset_info_in_ph_flag) { slice_cb_qp_offset se(v)slice_cr_qp_offset se(v) } } ... }

According to Tables 10 and 11, QP offsets can be signaled either in a PHor a SH to derive chroma QP values to achieve different levels of QPgranularity. In an example, chroma QP values can be derived as followsin Equations (7) and (8):QP′ _(Cb)=Clip3(−QpBdOffset, 63, qP _(Cb)+pps_cb_qp_offset+(chroma_qp_offset_info_in_ph_flag?ph_cb_qp_offset:slice_cb_qp_offset)+CuQpOffset_(Cb))+QpBdOffset   Eq.(7)QP′ _(Cr)=Clip3(−QpBdOffset, 63, qP _(Cr)+pps_cr_qp_offset+(chroma_qp_offset_info_in_ph_flag?ph_cr_qp_offset:slice_cr_qp_offset)+CuQpOffset_(Cr))+QpBdOffset   Eq.(8)As shown in Equations (7) and (8), when chroma_qp_offset_info_in_ph_flagis true or equal to the first value (e.g., 1), QP offsets (or chroma QPoffsets) in a PH (e.g., ph_cb_qp_offset and ph_cr_qp_offset) can besignaled. When chroma_qp_offset_info_in_ph_flag is not present or equalto the second value (e.g., 0), QP offsets (or chroma QP offsets) in a SH(e.g., slice_cb_qp_offset and slice_cr_qp_offset) can be signaled. Thus,depending on the value of chroma_qp_offset_info_in_ph_flag, only one QPoffset is used to derive chroma QP values (e.g., Qp′_(Cb) and Qp′_(Cr)).

Accordingly, when chroma_qp_offset_info_in_ph_flag is true or equal tothe first value (e.g., 1), a Cb quantization parameter (e.g., Qp′_(Cb))can be equal to a sum of a joint Cb offset and the quantizationparameter range offset (e.g., QpBdOffset). The joint Cb offset can bedetermined based on a sum of the Cb offset of the chroma QP offsets inthe PH level (e.g., ph_cb_qp_offset), the Cb component of the initialquantization parameter of the CU (e.g., qP_(Cb)), the Cb component ofthe quantization parameter offset of the CU in the PPS level (e.g.,pps_cb_qp_offset), and the Cb component of the coding unit quantizationparameter offset of the CU (e.g., CuQpOffset_(Cb)). The joint Cb offsetcan be determined based on the function Clip3 (x, y, z), and be largerthan or equal to the negative quantization parameter range offset (e.g.,−QpBdOffset) and be less than or equal to 63.

When chroma_qp_offset_info_in_ph_flag is true or equal to the firstvalue (e.g., 1), a Cr quantization parameter (e.g., Qp′_(Cr)) can beequal to a sum of a joint Cr offset and the quantization parameter rangeoffset (e.g., QpBdOffset). The joint Cr offset can be determined basedon a sum of the Cr offset of the chroma QP offsets in the PH level(e.g., ph_cr_qp_offset), the Cr component of the initial quantizationparameter of the CU (e.g., qP_(Cr)), the Cr component of thequantization parameter offset of the CU in the PPS level (e.g.,pp_cr_qp_offset), and the Cr component of the coding unit quantizationparameter offset of the CU (e.g., CuQpOffset_(Cr)). The joint Cr offsetcan be determined based on the function Clip3 (x, y, z), and be largerthan or equal to a negative quantization parameter range offset (e.g.,−QpBdOffset) and be less than or equal to 63.

When chroma_qp_offset_info_in_ph_flag is false or equal to the secondvalue (e.g., 0), a Cb quantization parameter (e.g., Qp′_(Cb)) can beequal to a sum of a joint Cb offset and the quantization parameter rangeoffset (e.g., QpBdOffset). The joint Cb offset can be determined basedon a sum of a Cb offset of the chroma QP offsets of the CU in the SHlevel (e.g., slice_cb_qp_offset), the Cb component of the initialquantization parameter of the CU (e.g., qP_(Cb)), the Cb component ofthe quantization parameter offset of the CU in the PPS level (e.g.,pps_cb_qp_offset), and the Cb component of the coding unit quantizationparameter offset of the CU (e.g., CuQpOffset_(Cb)). The joint Cb offsetcan be determined based on the function Clip3 (x, y, z), and be largerthan or equal to a negative quantization parameter range offset (e.g.,−QpBdOffset) and be less than or equal to 63.

When chroma_qp_offset_info_in_ph_flag is false or equal to the secondvalue (e.g., 0), a Cr quantization parameter (e.g., Qp′_(Cr)) can beequal to a sum of a joint Cr offset and the quantization parameter rangeoffset (e.g., QpBdOffset). The joint Cr offset can be determined basedon a sum of a Cr offset of the chroma QP offsets of the CU in the SHlevel (e.g., slice_cr_qp_offset), the Cr component of the initialquantization parameter of the CU (e.g., qP_(Cr)), the Cr component ofthe quantization parameter offset of the CU in the PPS level (e.g.,pp_cr_qp_offset), and the Cr component of the coding unit quantizationparameter offset of the CU (e.g., CuQpOffset_(Cr)). The joint Cr offsetcan be determined based on the function Clip3 (x, y, z), and be largerthan or equal to a negative quantization parameter range offset (e.g.,−QpBdOffset) and be less than or equal to 63.

In an embodiment, a QP offset of JCCR can be signalled in a PH. Forexample, exemplary corresponding syntax elements are shown in Table 12.

TABLE 12 Syntax elements to signal a QP offset of JCCR in PH Descriptorpicture_header_structure( ) { ... ph_joint_cb_cr_qp_offset se(v) ... }As shown in Table 12, ph_joint_cbcr_qp_offset can specify the offset tothe luma quantization parameter Qp′Y used for deriving Qp′CbCr. Thevalues of ph_joint_cbcr_qp_offset can be in the range of −12 to +12,inclusive. When not present, the values of ph_joint_cbcr_qp_offset canbe inferred to be equal to 0. The value ofpps_joint_cbcr_qp_offset+ph_joint_cbcr_qp_offset can be in the range of−12 to +12, inclusive.

In an embodiment, QP offsets of JCCR can be conditionally signaled in aPH based on chroma color format. For example, when only ChromaArrayTypeis not equal to 0, ph_joint_cbcr_qp_offset can be signaled. In otherwords, when no chroma component is present in the bitstream,ph_joint_cbcr_qp_offset is not signaled. Exemplary corresponding syntaxelements are illustrated in Table 13.

TABLE 13 Syntax elements to signal a QP offset of JCCR in PHconditionally Descriptor picture_header_structure( ) { ... if(ChromaArrayType !=0) { ph_joint_cb_cr_qp_offset se(v) ... } ... }As shown in Table 13, when ChromaArrayType is not equal to zero,ph_joint_cbcr_qp_offset can be signalled. ph_joint_cbcr_qp_offset canspecify the offset to the luma quantization parameter Qp′Y used forderiving Qp′CbCr. The values of ph_joint_cbcr_qp_offset can be in therange of −12 to +12, inclusive. When ph_joint_cbcr_qp_offset is notpresent, the values of ph_joint_cbcr_qp_offset can be inferred to beequal to 0. The value ofpps_joint_cbcr_qp_offset+ph_joint_cbcr_qp_offset can be in the range of−12 to +12, inclusive.

According to Tables 12 and 13, the QP offset of JCCR that is signaled ina PH and a SH can be applied to derive a QP value of JCCR in order toachieve better granularity of a QP. For example, a QP value of JCCR canbe derived as follows in Equation (9).Qp′CbCr=Clip3(−QpBdOffset, 63,qPCbCr+pps_joint_cbcr_qp_offset_value+ph_joint_cbcr_qp_offset+slice_joint_cbcr_qp_offset+CuQpOffsetCbCr)+QpBdOffset   Eq.(9)

According to Equation (9), a CbCr quantization parameter of thequantization parameters can be equal to a sum of a joint CbCr offset andthe quantization parameter range offset (e.g., QpBdOffset). The jointCbCr offset can be determined based on a sum of the CbCr offset of thechroma QP offsets in the PH level (e.g., ph_joint_cbcr_qp_offset), theCbCr quantization parameter of the CU (e.g., qPCbCr), the CbCrquantization parameter offset of the CU in the PPS level (e.g.,pps_joint_cbcr_qp_offset_value), the CbCr quantization parameter offsetof the CU in the SH level (e.g., slice_joint_cbcr_qp_offset), and theCbCr coding unit quantization parameter offset of the CU (e.g.,CuQpOffsetCbCr). The joint CbCr offset can be determined by the functionClip 3 (x, y, z) so as to be larger than or equal to the negativequantization parameter range offset (e.g., −QpBdOffset) and be less orequal to 63.

In an embodiment, QP offsets of JCCR can be signaled either in a PH or aSH to derive a chroma QP value according to a flag. The flag can also beapplied to condition the QP offset value. For example, the flag can bedefined as chroma_qp_offset_info_in_ph_flag.chroma_qp_offset_info_in_ph_flag equal to 1 can specify that chroma QPoffsets (e.g., ph_cb_qp_offset, and ph_cr_qp_offset) and QP offset ofJCCR information (e.g., ph_joint_cbcr_qp_offset) are present in the PHsyntax structure and not present in slice headers, where the sliceheaders refer to the PPS that do not contain a PH syntax structure.chroma_qp_offset_info_in_ph_flag equal to 0 can specify that QP deltainformation is not present in the PH syntax structure and may be presentin slice headers, where the slice header refer to the PPS that do notcontain a PH syntax structure. When chroma_qp_offset_info_in_ph_flag isnot present, it can be inferred to be equal to 0. Table 14 showsexemplary syntax elements to signal a QP offset of JCCR in a PH.

TABLE 14 Syntax elements to signal a QP offset of JCCR in PH Descriptorpicture_header_structure( ) { ... if (ChromaArrayType !=0) { if (chroma_qp_offset_info_in_ph_flag) { ph_cb_qp_offset se(v)ph_cr_qp_offset se(v) ph_joint_cbcr_qp_offset se(v) ... } } ... }As shown in Table 14, when chroma_qp_offset_info_in_ph_flag is presentor equal to the first value (e.g., 1), ph_joint_cbcr_qp_offset can besignalled, chroma_qp_offset_info_in_ph_flag can specify the offset tothe luma quantization parameter Qp′Y used for deriving Qp′CbCr. Thevalues of ph_joint_cbcr_qp_offset can be in the range of −12 to +12,inclusive. When ph_joint_cbcr_qp_offset is not present, the values ofph_joint_cbcr_qp_offset can be inferred to be equal to 0. The value ofpps_joint_cbcr_qp_offset+ph_joint_cbcr_qp_offset can be in the range of−12 to +12, inclusive.

Table 15 shows exemplary syntax elements to signal a QP offset of JCCRin a SH. As shown in Table 15, when chroma_qp_offset_info_in_ph_flag isnot present or equal to the second value (e.g., 0),slice_joint_cbcr_qp_offset can be signalled in the SH.

TABLE 15 syntax elements to signal a QP offset of JCCR in SH Descriptorslice_header( ) { ... if (ChromaArrayType !=0) { if (!chroma_qp_offset_info_in_ph_flag) { slice_cb_qp_offset se(v)slice_cr_qp_offset se(v) slice_joint_cbcr_qp_offset se(v) ... } } ... }

According to Tables 14 and 15, QP offsets can be signaled either in a PHor a SH to derive a JCCR QP value to achieve a different level of QPgranularity. For example, a CbCr component of a chroma QP value can bederived as follows in Equation (10).Qp′CbCr=Clip3(−QpBdOffset, 63,qPCbCr+pps_joint_cbcr_qp_offset_value+(chroma_qp_offset_info_in_ph_flag?ph_joint_cbcr_qp_offset:slice_joint_cbcr_qp_offset)+CuQpOffsetCbCr)+QpBdOffset  Eq. (10)As shown in Equation (10), when chroma_qp_offset_info_in_ph_flag is trueor equal to the first value (e.g., 1), ph_joint_cbcr_qp_offset issignalled. When chroma_qp_offset_info_in_ph_flag is false or equal tothe second value (e.g., 0), slice_joint_cbcr_qp_offset is signalled.Thus, depending on the value of chroma_qp_offset_info_in_ph_flag, onlyone QP offset is used to derive a JCCR QP value.

As shown in Equation (10), when chroma_qp_offset_info_in_ph_flag istrue, or equal to the first value (e.g., 1), a CbCr quantizationparameter (e.g. Qp′CbCr) can be equal to a sum of a joint CbCr offsetand the quantization parameter range offset (e.g., QpBdOffset). Thejoint CbCr offset can be determined based on a sum of the CbCr offset ofthe chroma QP offsets in the PH level (e.g., ph_joint_cbcr_qp_offset),the CbCr quantization parameter of the CU (e.g., qPCbCr), the CbCrquantization parameter offset of the CU in the PPS level (e.g.,pps_joint_cbcr_qp_offset_value), and the CbCr coding unit quantizationparameter offset of the CU (e.g., CuQpOffsetCbCr) in response to thesignal information being true. The joint CbCr offset can be determinedby the function Clip 3(x, y, z) so as to be larger than or equal to thenegative quantization parameter range offset (e.g., −QpBdOffset) and beless than or equal to 63.

When chroma_qp_offset_info_in_ph_flag is false or equal to the secondvalue (e.g., 0), a CbCr quantization parameter (e.g. Qp′CbCr) can beequal to a sum of a joint CbCr offset and the quantization parameterrange offset (e.g., QpBdOffset). The joint CbCr offset can be determinedbased on a sum of a CbCr offset of the chroma QP offsets of the CU inthe SH level (e.g., slice_joint_cbcr_qp_offset), the CbCr quantizationparameter of the CU (e.g., qPCbCr), the CbCr quantization parameteroffset of the CU in the PPS level (e.g.,pps_joint_cbcr_qp_offset_value), and the CbCr coding unit quantizationparameter offset of the CU (e.g., CuQpOffsetCbCr) in response to thesignal information being false. The joint CbCr offset can be determinedby the function Clip 3( ) so as to be larger than or equal to thenegative quantization parameter range offset (e.g., −QpBdOffset) and beless than or equal to 63.

FIGS. 7 and 8 show flow charts outlining a process (700) and a process(800) according to embodiments of the disclosure. The processes (700)and (800) can be used in determining quantization parameters for a CUbased on QP offsets in a PH level. In various embodiments, the processes(700) and (800) are executed by processing circuitry, such as theprocessing circuitry in the terminal devices (110), (120), (130) and(140), the processing circuitry that performs functions of the videoencoder (203), the processing circuitry that performs functions of thevideo decoder (210), the processing circuitry that performs functions ofthe video decoder (310), the processing circuitry that performsfunctions of the video encoder (403), and the like. In some embodiments,the processes (700) and (800) are implemented in software instructions,thus when the processing circuitry executes the software instructions,the processing circuitry performs the processes (700) and (800).

As shown in FIG. 7, the process (700) starts at (S701) and proceeds to(S710).

At (S710), syntax information of a coding block unit (CU) can be decodedfrom a coded video bitstream. The syntax information can be signaled ina picture header (PH) and include chroma quantization parameter (QP)offsets in a PH level, where the chroma QP offsets can include at leastone of a Cb offset, a Cr offset, and a CbCr offset.

In some embodiments, the syntax information can be signaled in thepicture header (PH) in response to a chroma array type not being equalto zero.

At (S720), quantization parameters for the CU can be determined based onthe chroma QP offsets in the PH level and a quantization parameter rangeoffset of the CU.

In order to determine the quantization parameters for the CU, a Cbcomponent of an initial quantization parameter of the CU can beobtained. A Cr component of the initial quantization parameter of the CUcan be obtained. A Cb component of a quantization parameter offset ofthe CU in a picture parameter set (PPS) level can be obtained. A Crcomponent of the quantization parameter offset of the CU in the PPSlevel can be obtained. A Cb component of a quantization parameter offsetof the CU in a slice header (SH) level can be obtained. A Cr componentof the quantization parameter offset of the CU in the SH level can beobtained. A Cb component of a coding unit quantization parameter offsetof the CU can be obtained. A Cr component of the coding unitquantization parameter offset of the CU can be obtained.

In some embodiments, a Cb quantization parameter of the quantizationparameters can be determined based on the QP offsets in the PH level andthe quantization parameter range offset of the CU. The Cb quantizationparameter can be equal to a sum of a joint Cb offset and thequantization parameter range offset. The joint Cb offset can bedetermined based on a sum of the Cb offset of the chroma QP offsets inthe PH level, the Cb component of the initial quantization parameter ofthe CU, the Cb component of the quantization parameter offset of the CUin the PPS level, the Cb component of the quantization parameter offsetof the CU in the SH level, and the Cb component of the coding unitquantization parameter offset of the CU. The joint Cb offset can belarger than or equal to a negative quantization parameter range offsetand be less than or equal to 63.

In addition, a Cr quantization parameter of the quantization parameterscan be determined based on the QP offsets in the PH level and thequantization parameter range offset of the CU. The Cr quantizationparameter can be equal to a sum of a joint Cr offset and thequantization parameter range offset. The joint Cr offset can bedetermined based on a sum of the Cr offset of the chroma QP offsets inthe PH level, the Cr component of the initial quantization parameter ofthe CU, the Cr component of the quantization parameter offset of the CUin the PPS level, the Cr component of the quantization parameter offsetof the CU in the SH level, and the Cr component of the coding unitquantization parameter offset of the CU, where the joint Cr offset canbe larger than or equal to a negative quantization parameter rangeoffset and be less than or equal to 63.

In some embodiments, a CbCr quantization parameter of the CU can bedetermined. A CbCr quantization parameter offset of the CU in a pictureparameter set (PPS) level can be obtained. A CbCr quantization parameteroffset of the CU in a slice header (SH) level can be obtained. A CbCrcoding unit quantization parameter offset of the CU can be obtained.

In some embodiments, a CbCr quantization parameter of the quantizationparameters can be determined based on the QP offsets in the PH level andthe quantization parameter range offset of the CU. The CbCr quantizationparameter can be equal to a sum of a joint CbCr offset and thequantization parameter range offset. The joint CbCr offset can bedetermined based on a sum of the CbCr offset of the chroma QP offsets inthe PH level, the CbCr quantization parameter of the CU, the CbCrquantization parameter offset of the CU in the PPS level, the CbCrquantization parameter offset of the CU in the SH level, and the CbCrcoding unit quantization parameter offset of the CU. The joint CbCroffset can be larger than or equal to a negative quantization parameterrange offset and be less or equal to 63.

In some embodiments, a sum of the Cb component of the quantizationparameter offset of the CU in the PPS level and the Cb offset of thechroma QP offsets in the PH level can be in a range of −12 and +12. Inaddition, a sum of the Cr component of the quantization parameter offsetof the CU in the PPS level and the Cr offset of the chroma QP offsets inthe PH level can be in a range of −12 and +12. A sum of a CbCrquantization parameter offset of the CU in the PPS level and the CbCroffset of the chroma QP offsets in the PH level can be in a range of −12and +12.

As shown in FIG. 8, the process (800) starts at (S801) and proceeds to(S810).

At (S810), signaling information from a coded video bitstream can beacquired.

At (S820), first syntax information of a coding block unit (CU) from thecoded video bitstream can be decoded in response to the signalinginformation being a first value. The first syntax information can besignaled in a picture header (PH) and include chroma quantizationparameter (QP) offsets in a PH level. The chroma QP offsets in the PHlevel can include at least one of a Cb offset, a Cr offset, and a CbCroffset.

In some embodiments, second syntax information of the CU can be decodedfrom the coded video bitstream in response to the signaling informationbeing a second value. The second syntax information can be signaled in aslice header (SH) and include chroma quantization parameter (QP) offsetsin a SH level. The chroma QP offsets in the SH level can include atleast one of a Cb offset, a Cr offset, and a CbCr offset. Thequantization parameters for the CU can be further determined based onthe QP offsets in the SH level and the quantization parameter rangeoffset of the CU.

In some embodiments, the first syntax information can be signaled in thepicture header (PH) in response to a chroma array type not beingmonochrome or not being a chroma format 4:4;4 with a separate colorplane flag equal to 1. The chroma type can be determined based on chromaarray type information (e.g., ChromaArrayType value equal to 0), asillustrated in Table 6 for example.

In some embodiments, the second syntax information can be signaled inthe SH in response to the chroma array type not being monochrome or notbeing the chroma format 4:4;4 with the separate color plane flag equalto 1. The chroma type can be determined based on chroma array typeinformation (e.g., ChromaArrayType value equal to 0), as illustrated inTable 6 for example.

At (S830), quantization parameters for the CU can be subsequentlydetermined based on the QP offsets in the PH level and a quantizationparameter range offset of the CU.

In order to determine the quantization parameters for the CU, a Cbcomponent of an initial quantization parameter of the CU can beobtained. A Cr component of the initial quantization parameter of the CUcan be obtained. A Cb component of a quantization parameter offset ofthe CU in a picture parameter set (PPS) level can be obtained. A Crcomponent of the quantization parameter offset of the CU in the PPSlevel can be obtained. A Cb component of a coding unit quantizationparameter offset of the CU can be obtained. A Cr component of the codingunit quantization parameter offset of the CU can be obtained.

In some embodiments, a Cb quantization parameter can be determined basedon the QP offsets in the PH level and the quantization parameter rangeoffset of the CU. The Cb quantization parameter can be equal to a sum ofa joint Cb offset and the quantization parameter range offset. The jointCb offset can be determined based on a sum of the Cb offset of thechroma QP offsets in the PH level, the Cb component of the initialquantization parameter of the CU, the Cb component of the quantizationparameter offset of the CU in the PPS level, and the Cb component of thecoding unit quantization parameter offset of the CU in response to thesignaling information being the first value. The joint Cb offset can belarger than or equal to a negative quantization parameter range offsetand be less than or equal to 63.

In addition, a Cr quantization parameter can be determined based on theQP offsets in the PH level and the quantization parameter range offsetof the CU. The Cr quantization parameter can be equal to a sum of ajoint Cr offset and the quantization parameter range offset. The jointCr offset can be determined based on a sum of the Cr offset of thechroma QP offsets in the PH level, the Cr component of the initialquantization parameter of the CU, the Cr component of the quantizationparameter offset of the CU in the PPS level, and the Cr component of thecoding unit quantization parameter offset of the CU in response to thesignaling information being the first value. The joint Cr offset can belarger than or equal to a negative quantization parameter range offsetand be less than or equal to 63.

Moreover, a CbCr quantization parameter of the CU can be obtained. ACbCr quantization parameter offset of the CU in a picture parameter set(PPS) level can be obtained. A CbCr coding unit quantization parameteroffset of the CU can be obtained.

In some embodiments, a CbCr quantization parameter can be determinedbased on the QP offsets in the PH level and the quantization parameterrange offset of the CU. The CbCr quantization parameter can be equal toa sum of a joint CbCr offset and the quantization parameter rangeoffset. The joint CbCr offset can be determined based on a sum of theCbCr offset of the chroma QP offsets in the PH level, the CbCrquantization parameter of the CU, the CbCr quantization parameter offsetof the CU in the PPS level, and the CbCr coding unit quantizationparameter offset of the CU in response to the signal information beingthe first value. The joint CbCr offset can be larger than or equal to anegative quantization parameter range offset and being less than orequal to 63.

In some embodiments, a Cb quantization parameter can be determined basedon the chroma QP offsets in the SH level and the quantization parameterrange offset of the CU. The Cb quantization parameter can be equal to asum of a joint Cb offset and the quantization parameter range offset.The joint Cb offset can be determined based on a sum of the Cb offset ofthe chroma QP offsets of the CU in the SH level, the Cb component of theinitial quantization parameter of the CU, the Cb component of thequantization parameter offset of the CU in the PPS level, and the Cbcomponent of the coding unit quantization parameter offset of the CU inresponse to the signaling information being the second value. The jointCb offset can be larger than or equal to a negative quantizationparameter range offset and be less than or equal to 63.

In some embodiments, a Cr quantization parameter can be determined basedon the chroma QP offsets in the SH level and the quantization parameterrange offset of the CU. The Cr quantization parameter can be equal to asum of a joint Cr offset and the quantization parameter range offset.The joint Cr offset can be determined based on a sum of the Cr offset ofthe chroma QP offsets of the CU in the SH level, the Cr component of theinitial quantization parameter of the CU, the Cr component of thequantization parameter offset of the CU in the PPS level, and the Crcomponent of the coding unit quantization parameter offset of the CU inresponse to being the signaling information being the second value. Thejoint Cr offset can be larger than or equal to a negative quantizationparameter range offset and be less than or equal to 63.

In addition, a CbCr quantization parameter based on the chroma QPoffsets in the SH level and the quantization parameter range offset ofthe CU, wherein: the CbCr quantization parameter is equal to a sum of ajoint CbCr offset and the quantization parameter range offset, and thejoint CbCr offset can be determined based on a sum of the CbCr offset ofthe chroma QP offsets of the CU in the SH level, the CbCr quantizationparameter of the CU, the CbCr quantization parameter offset of the CU inthe PPS level, and the CbCr coding unit quantization parameter offset ofthe CU in response to the signaling information being the second value.The joint CbCr offset can be larger than or equal to a negativequantization parameter range offset and be less than or equal to 63.

It should be noted that methods in the present disclosure can be usedseparately or combined in any order. Further, each of the methods (orembodiments), encoder, and decoder can be implemented by processingcircuitry (e.g., one or more processors or one or more integratedcircuits). In one example, the one or more processors execute a programthat is stored in a non-transitory computer-readable medium.

The techniques described above, can be implemented as computer softwareusing computer-readable instructions and physically stored in one ormore computer-readable media. For example, FIG. 9 shows a computersystem (1500) suitable for implementing certain embodiments (e.g.,processes (700) and (800) of the disclosed subject matter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by one or more computer central processingunits (CPUs), Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 9 for computer system (1500) are exemplaryin nature and are not intended to suggest any limitation as to the scopeof use or functionality of the computer software implementingembodiments of the present disclosure. Neither should the configurationof components be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system (1500).

Computer system (1500) may include certain human interface inputdevices. Such a human interface input device may be responsive to inputby one or more human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard (1501), mouse (1502), trackpad (1503), touchscreen (1510), data-glove (not shown), joystick (1505), microphone(1506), scanner (1507), camera (1508).

Computer system (1500) may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen (1510), data-glove (not shown), or joystick (1505), butthere can also be tactile feedback devices that do not serve as inputdevices), audio output devices (such as: speakers (1509), headphones(not depicted)), visual output devices (such as screens (1510) toinclude CRT screens, LCD screens, plasma screens, OLED screens, eachwith or without touch-screen input capability, each with or withouttactile feedback capability—some of which may be capable to output twodimensional visual output or more than three dimensional output throughmeans such as stereographic output; virtual-reality glasses (notdepicted), holographic displays and smoke tanks (not depicted)), andprinters (not depicted).

Computer system (1500) can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW(1520) with CD/DVD or the like media (1521), thumb-drive (1522),removable hard drive or solid state drive (1523), legacy magnetic mediasuch as tape and floppy disc (not depicted), specialized ROM/ASIC/PLDbased devices such as security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system (1500) can also include an interface to one or morecommunication networks. Networks can for example be wireless, wireline,optical. Networks can further be local, wide-area, metropolitan,vehicular and industrial, real-time, delay-tolerant, and so on. Examplesof networks include local area networks such as Ethernet, wireless LANs,cellular networks to include GSM, 3G, 4G, 5G, LTE and the like, TVwireline or wireless wide area digital networks to include cable TV,satellite TV, and terrestrial broadcast TV, vehicular and industrial toinclude CANBus, and so forth. Certain networks commonly require externalnetwork interface adapters that attached to certain general purpose dataports or peripheral buses (1549) (such as, for example USB ports of thecomputer system (1500)); others are commonly integrated into the core ofthe computer system (1500) by attachment to a system bus as describedbelow (for example Ethernet interface into a PC computer system orcellular network interface into a smartphone computer system). Using anyof these networks, computer system (1500) can communicate with otherentities. Such communication can be uni-directional, receive only (forexample, broadcast TV), uni-directional send-only (for example CANbus tocertain CANbus devices), or bi-directional, for example to othercomputer systems using local or wide area digital networks. Certainprotocols and protocol stacks can be used on each of those networks andnetwork interfaces as described above.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core (1540) of thecomputer system (1500).

The core (1540) can include one or more Central Processing Units (CPU)(1541), Graphics Processing Units (GPU) (1542), specialized programmableprocessing units in the form of Field Programmable Gate Areas (FPGA)(1543), hardware accelerators for certain tasks (1544), and so forth.These devices, along with Read-only memory (ROM) (1545), Random-accessmemory (1546), internal mass storage such as internal non-useraccessible hard drives, SSDs, and the like (1547), may be connectedthrough a system bus (1548). In some computer systems, the system bus(1548) can be accessible in the form of one or more physical plugs toenable extensions by additional CPUs, GPU, and the like. The peripheraldevices can be attached either directly to the core's system bus (1548),or through a peripheral bus (1549). Architectures for a peripheral businclude PCI, USB, and the like.

CPUs (1541), GPUs (1542), FPGAs (1543), and accelerators (1544) canexecute certain instructions that, in combination, can make up theaforementioned computer code. That computer code can be stored in ROM(1545) or RAM (1546). Transitional data can be also be stored in RAM(1546), whereas permanent data can be stored for example, in theinternal mass storage (1547). Fast storage and retrieve to any of thememory devices can be enabled through the use of cache memory, that canbe closely associated with one or more CPU (1541), GPU (1542), massstorage (1547), ROM (1545), RAM (1546), and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture (1500), and specifically the core (1540) can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core (1540) that are of non-transitorynature, such as core-internal mass storage (1547) or ROM (1545). Thesoftware implementing various embodiments of the present disclosure canbe stored in such devices and executed by core (1540). Acomputer-readable medium can include one or more memory devices orchips, according to particular needs. The software can cause the core(1540) and specifically the processors therein (including CPU, GPU,FPGA, and the like) to execute particular processes or particular partsof particular processes described herein, including defining datastructures stored in RAM (1546) and modifying such data structuresaccording to the processes defined by the software. In addition or as analternative, the computer system can provide functionality as a resultof logic hardwired or otherwise embodied in a circuit (for example:accelerator (1544)), which can operate in place of or together withsoftware to execute particular processes or particular parts ofparticular processes described herein. Reference to software canencompass logic, and vice versa, where appropriate. Reference to acomputer-readable media can encompass a circuit (such as an integratedcircuit (IC)) storing software for execution, a circuit embodying logicfor execution, or both, where appropriate. The present disclosureencompasses any suitable combination of hardware and software.

Appendix A: Acronyms

HEVC: High Efficiency Video Coding

HDR: High Dynamic Range

SDR: Standard Dynamic Range

VVC: Versatile Video Coding

JVET: Joint Video Exploration Team

TU: Transform Unit

SPS: Sequence Parameter Setting

PPS: Picture Parameter Setting

PH: Picture Header

SH: Slice Header

QP: Quantization Parameter

JCCR: Joint Cb Cr Residual coding

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof.

What is claimed is:
 1. A method of video decoding performed in a videodecoder, the method comprising: decoding syntax information of a codingunit (CU) from a coded video bitstream, the syntax information beingsignaled in a picture header (PH) and including chroma quantizationparameter (QP) offsets in a PH level, the chroma QP offsets in the PHlevel including at least one of a Cb offset, a Cr offset, and a CbCroffset; and determining quantization parameters for the CU based onjoint chroma QP offsets signaled at a plurality levels in the codedvideo bitstream and a quantization parameter range offset of the CU, thejoint chroma QP offsets including the chroma QP offsets in the PH level,wherein the syntax information is signaled in the PH in response to achroma array type not being monochrome or not being a chroma format4:4:4 with a separate color plane flag equal to
 1. 2. The method ofclaim 1, wherein the determining the quantization parameters for the CUcomprises: obtaining a Cb component of an initial quantization parameterof the CU; obtaining a Cr component of the initial quantizationparameter of the CU; obtaining a Cb component of a quantizationparameter offset of the CU in a picture parameter set (PPS) level;obtaining a Cr component of the quantization parameter offset of the CUin the PPS level; obtaining a Cb component of a quantization parameteroffset of the CU in a slice header (SH) level; obtaining a Cr componentof the quantization parameter offset of the CU in the SH level;obtaining a Cb component of a coding unit quantization parameter offsetof the CU; and obtaining a Cr component of the coding unit quantizationparameter offset of the CU.
 3. The method of claim 2, wherein thedetermining the quantization parameters for the CU comprises:determining a Cb quantization parameter of the quantization parametersto be equal to a sum of a joint Cb offset of the joint chroma QP offsetsand the quantization parameter range offset, wherein the joint Cb offsetof the joint chroma QP offsets is based on a sum of the Cb offset of thechroma QP offsets in the PH level, the Cb component of the initialquantization parameter of the CU, the Cb component of the quantizationparameter offset of the CU in the PPS level, the Cb component of thequantization parameter offset of the CU in the SH level, and the Cbcomponent of the coding unit quantization parameter offset of the CU,the joint Cb offset of the joint chroma QP offsets being larger than orequal to a negative quantization parameter range offset and being lessthan or equal to
 63. 4. The method of claim 2, wherein the determiningthe quantization parameters for the CU comprises: determining a Crquantization parameter of the quantization parameters to be equal to asum of a joint Cr offset of the joint chroma QP offsets and thequantization parameter range offset, wherein the joint Cr offset of thejoint chroma QP offsets is based on a sum of the Cr offset of the chromaQP offsets in the PH level, the Cr component of the initial quantizationparameter of the CU, the Cr component of the quantization parameteroffset of the CU in the PPS level, the Cr component of the quantizationparameter offset of the CU in the SH level, and the Cr component of thecoding unit quantization parameter offset of the CU, the joint Cr offsetof the joint chroma QP offsets being larger than or equal to a negativequantization parameter range offset and being less than or equal to 63.5. The method of claim 1, wherein the determining the quantizationparameters for the CU comprises: obtaining a CbCr quantization parameterof the CU; obtaining a CbCr quantization parameter offset of the CU in apicture parameter set (PPS) level; obtaining a CbCr quantizationparameter offset of the CU in a slice header (SH) level; and obtaining aCbCr coding unit quantization parameter offset of the CU.
 6. The methodof claim 5, wherein the determining the quantization parameters for theCU comprises: determining a CbCr quantization parameter of thequantization parameters to be equal to a sum of a joint CbCr offset ofthe joint chroma QP offsets and the quantization parameter range offset,wherein the joint CbCr offset of the joint chroma QP offsets is based ona sum of the CbCr offset of the chroma QP offsets in the PH level, theCbCr quantization parameter of the CU, the CbCr quantization parameteroffset of the CU in the PPS level, the CbCr quantization parameteroffset of the CU in the SH level, and the CbCr coding unit quantizationparameter offset of the CU, the joint CbCr offset of the joint chroma QPoffsets being larger than or equal to a negative quantization parameterrange offset and being less or equal to
 63. 7. The method of claim 2,wherein: a sum of the Cb component of the quantization parameter offsetof the CU in the PPS level and the Cb offset of the chroma QP offsets inthe PH level is in a range of −12 and +12, a sum of the Cr component ofthe quantization parameter offset of the CU in the PPS level and the Croffset of the chroma QP offsets in the PH level is in a range of −12 and+12, and a sum of a CbCr quantization parameter offset of the CU in thePPS level and the CbCr offset of the chroma QP offsets in the PH levelis in a range of −12 and +12.
 8. The method of claim 1, wherein thejoint chroma QP offsets further includes an initial quantizationparameter of the CU, a quantization parameter offset of the CU in apicture parameter setting (PPS) level, a quantization parameter offsetof the CU in a slice header (SH) level, and a coding unit quantizationparameter offset of the CU.
 9. A method of video decoding performed in avideo decoder, the method comprising: acquiring signaling informationfrom a coded video bitstream; decoding first syntax information of acoding unit (CU) from the coded video bitstream in response to thesignaling information being a first value, the first syntax informationbeing signaled in a picture header (PH) and including chromaquantization parameter (QP) offsets in a PH level, the chroma QP offsetsin the PH level including at least one of a Cb offset, a Cr offset, anda CbCr offset; and determining quantization parameters for the CU basedon joint chroma QP offsets signaled at a plurality levels in the codedvideo bitstream and a quantization parameter range offset of the CU, thejoint chroma QP offsets including the chroma QP offsets in the PH levelin response to the signaling information being the first value, whereinthe syntax information is signaled in the PH in response to a chromaarray type not being monochrome or not being a chroma format 4:4:4 witha separate color plane flag equal to
 1. 10. The method of claim 9,further comprising: decoding second syntax information of the CU fromthe coded video bitstream in response to the signaling information beinga second value, the second syntax information being signaled in a sliceheader (SH) and including chroma QP offsets in a SH level, the chroma QPoffsets in the SH level including at least one of a Cb offset, a Croffset, and a CbCr offset; and determining the quantization parametersfor the CU based on the joint chroma QP offsets and the quantizationparameter range offset of the CU, the joint chroma QP offsets includingthe chroma QP offsets in the SH level in response to the signalinginformation being the second value.
 11. The method of claim 10, wherein:the first syntax information is signaled in the picture header (PH) inresponse to a chroma array type not being monochrome and not being achroma format 4:4:4 with a separate color plane flag equal to 1, and thesecond syntax information is signaled in the SH in response to thechroma array type not being monochrome and not being the chroma format4:4:4 with the separate color plane flag equal to
 1. 12. The method ofclaim 10, wherein the determining the quantization parameters for the CUcomprises: obtaining a Cb component of an initial quantization parameterof the CU; obtaining a Cr component of the initial quantizationparameter of the CU; obtaining a Cb component of a quantizationparameter offset of the CU in a picture parameter set (PPS) level;obtaining the Cr component of the quantization parameter offset of theCU in the SH level; obtaining a Cb component of a coding unitquantization parameter offset of the CU; and obtaining a Cr component ofthe coding unit quantization parameter offset of the CU.
 13. The methodof claim 12, wherein the determining the quantization parameters for theCU comprises: determining a Cb quantization parameter of thequantization parameters to be equal to a sum of a joint Cb offset of thejoint chroma QP offsets and the quantization parameter range offset,wherein the joint Cb offset of the joint chroma QP offsets is based on asum of the Cb offset of the chroma QP offsets in the PH level, the Cbcomponent of the initial quantization parameter of the CU, the Cbcomponent of the quantization parameter offset of the CU in the PPSlevel, and the Cb component of the coding unit quantization parameteroffset of the CU in response to the signaling information being thefirst value, the joint Cb offset being larger than or equal to anegative quantization parameter range offset and being less than orequal to
 63. 14. The method of claim 12, wherein the determining thequantization parameters for the CU comprises: determining a Crquantization parameter of the quantization parameters to be equal to asum of a joint Cr offset of the joint chroma QP offsets and thequantization parameter range offset, wherein the joint Cr offset of thejoint chroma QP offsets is based on a sum of the Cr offset of the chromaQP offsets in the PH level, the Cr component of the initial quantizationparameter of the CU, the Cr component of the quantization parameteroffset of the CU in the PPS level, and the Cr component of the codingunit quantization parameter offset of the CU in response to thesignaling information being the first value, the joint Cr offset beinglarger than or equal to a negative quantization parameter range offsetand being less than or equal to
 63. 15. The method of claim 10, whereinthe determining the quantization parameters for the CU comprises:obtaining a CbCr quantization parameter of the CU; obtaining a CbCrquantization parameter offset of the CU in a picture parameter set (PPS)level; and obtaining a CbCr coding unit quantization parameter offset ofthe CU.
 16. The method of claim 15, wherein the determining thequantization parameters for the CU comprises: determining a CbCrquantization parameter of the quantization parameters to be equal to asum of a joint CbCr offset of the joint chroma QP offsets and thequantization parameter range offset, wherein the joint CbCr offset ofthe joint chroma QP offsets is based on a sum of the CbCr offset of thechroma QP offsets in the PH level, the CbCr quantization parameter ofthe CU, the CbCr quantization parameter offset of the CU in the PPSlevel, and the CbCr coding unit quantization parameter offset of the CUin response to the signaling information being the first value, thejoint CbCr offset being larger than or equal to a negative quantizationparameter range offset and being less than or equal to
 63. 17. Themethod of claim 12, wherein the determining the quantization parametersfor the CU comprises: determining a Cb quantization parameter of thequantization parameters to be equal to a sum of a joint Cb offset of thejoint chroma QP offsets and the quantization parameter range offset,wherein the joint Cb offset of the joint chroma QP offsets is based on asum of the Cb offset of the chroma QP offsets of the CU in the SH level,the Cb component of the initial quantization parameter of the CU, the Cbcomponent of the quantization parameter offset of the CU in the PPSlevel, and the Cb component of the coding unit quantization parameteroffset of the CU in response to the signaling information being thesecond value, the joint Cb offset being larger than or equal to anegative quantization parameter range offset and being less than orequal to
 63. 18. The method of claim 12, wherein the determining thequantization parameters for the CU comprises: determining a Crquantization parameter of the quantization parameters to be equal to asum of a joint Cr offset of the joint chroma QP offsets and thequantization parameter range offset, wherein the joint Cr offset of thejoint chroma QP offsets is based on a sum of the Cr offset of the chromaQP offsets of the CU in the SH level, the Cr component of the initialquantization parameter of the CU, the Cr component of the quantizationparameter offset of the CU in the PPS level, and the Cr component of thecoding unit quantization parameter offset of the CU in response to beingthe signaling information being the second value, the joint Cr offsetbeing larger than or equal to a negative quantization parameter rangeoffset and being less than or equal to
 63. 19. The method of claim 15,wherein the determining the quantization parameters for the CUcomprises: determining a CbCr quantization parameter of the quantizationparameters to be equal to a sum of a joint CbCr offset of the jointchroma QP offsets and the quantization parameter range offset, whereinthe joint CbCr offset of the joint chroma QP offsets is based on a sumof the CbCr offset of the chroma QP offsets of the CU in the SH level,the CbCr quantization parameter of the CU, the CbCr quantizationparameter offset of the CU in the PPS level, and the CbCr coding unitquantization parameter offset of the CU in response to the signalinginformation being the second value, the joint CbCr offset being largerthan or equal to a negative quantization parameter range offset andbeing less than or equal to
 63. 20. An apparatus, comprising: processingcircuitry configured to: decode syntax information of a coding unit (CU)from a coded video bitstream, the syntax information being signaled in apicture header (PH) and including chroma quantization parameter (QP)offsets in a PH level, the chroma QP offsets in the PH level includingat least one of a Cb offset, a Cr offset, and a CbCr offset; anddetermine quantization parameters for the CU based on joint chroma QPoffsets signaled at a plurality levels in the coded video bitstream anda quantization parameter range offset of the CU, the joint chroma QPoffsets including the chroma QP offsets in the PH level, wherein thesyntax information is signaled in the PH in response to a chroma arraytype not being monochrome or not being a chroma format 4:4:4 with aseparate color plane flag equal to 1.